Chapter 21

The estimated increased yield of the income tax for 1909-1910 on these lines was Â£2,500,000, which excluded the abatements allowed for improvements. The super-tax was estimated to yield a sum of Â£500,000, which would be increased ultimately to Â£2,500,000, when all returns and assessments were made.

The following accounts show the operation of the same system of taxation in other countries:â€”2

Austria.â€”The income tax dates from 1849, but the existing tax, which is arranged on a progressive system, came into force on the 1st of January 1898. The tax is levied on net income, deductions from the gross income being allowed for upkeep of business, houses and lands, for premiums paid for insurance against injuries, for interest on business and private debts, and for payment of taxes other than income tax. Incomes under Â£50 a year are exempt, the rate of taxation at the first stage (Â£52) being 0.6 of the income; at the twelfth stage (Â£100) the rate is 1%, at the twenty-seventh stage (Â£300) it rises to 2%, at the forty-third stage (Â£1000) it is 3%, and at the fifty-sixth (Â£2500) it is 3Â½%; an income of Â£4000 pays 4%; from Â£4000 up to Â£8333 per annum progression rises at Â£166 a step, and for every step Â£8, 6s. 8d. taxation is assessed. Incomes between Â£8333 and Â£8750 pay Â£387, 10s.; incomes over Â£8750 are taxed Â£20, 6s. 8d. at each successive stage of Â£417, 10s. Certain persons are exempt from the tax, viz.:â€”(a) the emperor; (b) members of the imperial family, as far as regards such sums as they receive as allowances; (c) the diplomatic corps, the consular corps who are not Austrian citizens, and the official staffs and foreign servants of the embassies, legations and consulates; (d) such people as are exempted by treaty or by the law of nations; (e) people in possession of pensions from the Order of Maria Theresa, and those who receive pensions on account of wounds or the pension attached to the medal for bravery, are exempted as far as the pensions are concerned; (f) officers, chaplains and men of the army and navy have no tax levied on their pay; (g) all other military persons, and such people as are included in the scheme of mobilization are exempted from any tax on their pay. Special allowances are made for incomes derived from labour, either physical or mental, as well as for a family with several children. There are also special exemptions in certain cases where the annual income does not exceed Â£4167, 10s., viz.â€”(a) special charges for educating children who may be blind, deaf, dumb or crippled; (b) expense in maintaining poor relations; (c) perpetual illness; (d) debts; (e) special misfortunes caused by fire or floods; (f) being called out for military service. The tax is assessed usually on a direct return from the individual taxpayer, except in the cases of fixed salaries and wages, on which the tax is collected from the employer, who either deducts it from the salary of the employee or pays it out of his own pocket. The tax, which is assessed on the income of the previous year, is paid direct to the collectorâ€™s office in two instalmentsâ€”one on the 1st of June and the other on the 1st of December.Belgium.â€”No income tax proper exists in Belgium, but there is a state tax of 2% on the dividends of joint stock companies.Denmark.â€”Income tax is levied under a law of the 15th of May 1903. Incomes under 2000 kroner pay a tax of 1.3%; under 3000 kroner, 1.4%; under 4000 kroner, 1.5%; under 6000 kroner, 1.6%; under 8000 kroner, 1.7%; under 10,000 kroner, 1.8%; under 15,000 kroner, 1.9%; under 20,000 kroner, 2.0% and for every additional 10,000 kroner up to 100,000 kroner 1%, incomes of 100,000 kroner and upwards paying 2.5%. Exempt from the duty areâ€”the king, members of the royal family and the civil list; the legations, staffs and consular officers of foreign powers (not being Danish subjects); foreigners temporarily resident in the country; mortgage societies, credit institutions, savings and loan banks. The increase in capital resulting from an increase in value of properties is not deemed incomeâ€”on the other hand no deduction in income is made if such properties decrease in valueâ€”nor are daily payments and travelling expenses received for the transaction of business on public service, if the person has thereby been obliged to reside outside his own parish. Certain deductions can be made in calculating incomeâ€”such as working expenses, office expenses, pensions and other burthens, amounts paid for direct taxation, dues to commune and church, tithe, tenant and farming charges, heirsâ€™ allowances and similar burthens; interest on mortgages and other debts, and what has been spent for necessary maintenance or insurance of the property of the taxpayer. There are also certain exemptions with respect to companies not having an establishment in the country.France.â€”There is no income tax in France corresponding exactly to that levied in the United Kingdom. There are certain direct taxes, such as the taxes on buildings,personnelle mobiliÃ¨re, and doors and windows (impÃ´ts de rÃ©partition)â€”the tax levied on income from land and from all trades and professions (impÃ´ts de quotitÃ©) which bear a certain resemblance to portions of the British income tax (seeFrance:Finance). From time to time a graduated income tax has been under discussion in the French Chambers, the proposal being to substitute such a tax for the existing (personnelle mobiliÃ¨re) and doors and windows taxes, but no agreement on the matter has been reached.German Empire.â€”In Prussia the income tax is levied under a law of the 24th of June 1891. All persons with incomes of over Â£150 per annum are required to send in an annual declaration of their full income, divided according to four main sourcesâ€”(a) capital; (b) landed property; (c) trade and industry; (d) employment bringing gain, this latter including the salary or wages of workmen, servants and industrial assistants, military persons and officials; also the receipts of authors, artists, scientists, teachers and tutors. Liability for income tax, however, begins with an income of Â£45, and rises by a regular system of progression, the rate being about 3% of the income. Thus an income of more than Â£45, but under Â£52, 10s. pays a tax of 6s. and so on up to Â£475, an income over that sum but under Â£525 paying a tax of 15s. Incomes over Â£525 rise by steps of Â£50 up to Â£1525, for every step Â£1, 10s. being paid. Incomes between Â£1526 and Â£1600 rise by steps of Â£75, Â£3 being paid for every step. Between Â£1601 and Â£3900, the steps are Â£100, and the tax Â£4 a step; from Â£3901 to Â£5000 the steps are the same (Â£100), but the tax is Â£5 a step. There is also a supplementary tax on property of about1â„20th% of the assessed value. This supplementary tax is not levied on those whose taxable property does not exceed a total value of Â£300, nor on those whose annual income does not exceed Â£45, if the total value of their taxable property does not exceed Â£1000, nor on women who have members of their own family under age to maintain, nor on orphans under age, nor on persons incapable of earning incomes if their taxable property does not exceed Â£1000 nor their income Â£60. There are a number of exemptions from the income tax, some of the more important beingâ€”(a) the military incomes of non-commissioned officers and privates, also of all persons on the active list of the army or navy as long as they belong to a unit in war formation; (b) extraordinary receipts from inheritances, presents, insurances, from the sale of real estate not undertaken for purposes of industry or speculation, and similar profits (all of which are reckoned as increases of capital); (c) expenses incurred for the purpose of acquiring, assuring and maintaining income; (d) interest on debts; (e) the regular annual depreciation arising from wear of buildings, machines, tools, &c., in so far as they are not included under working expenses; (f) the contributions which taxpayers are compelled by law or agreement to pay to invalid, accident, old age insurance, widow, orphan and pension funds; (g) insurance premiums. Moreover, persons liable to taxation with an income of not more than Â£150 may deduct from that income Â£2, 10s. for every member of their family under fourteen years of age, and abatement is also allowed to persons with incomes up to Â£475 whose solvency has been unfavourably affected by adverse economic circumstances. The income tax is both levied at the source (as in the case of companies) and assessed on a direct return by the taxpayer of his income from all sources. Salaries are not taxed before payment. Fixed receipts are assessed according to their amount for the taxation year in which the assessment is made, and variable incomes on anaverage of the three years immediately preceding the assessment. The income tax and the supplementary tax are collected in the first half of the second month of each quarter by the communities (Gemeinden) who bear the whole cost.In Saxony a graduated tax is in force on all incomes of Â£20 per annum and upwards. All corporate bodies and individuals who derive their income or any portion of it from Saxony are liable to the extent of that income, except those serving religious, charitable or public purposes. Incomes between Â£20 and Â£5000 are divided into 118 classes, in which the rate rises progressively. From Â£500 to Â£5000 the classes rise by Â£50, and above Â£5000 by Â£100. The rate of income tax begins at Â¼%,i.e.1s. on an income of Â£20. An abatement is allowed to those whose incomes do not exceed Â£155 of Â£2, 10s. for each child between the ages of six and fourteen years, provided such abatements do not reduce the income by more than one class. In the case of persons with incomes not exceeding Â£290 abatement (not exceeding three classes) is allowedâ€”(a) when the support of children or indigent relations involves a burden of such a nature as to affect the general standard of living; (b) on account of long-continued illness, involving heavy expense; and, on restoration to health, temporary decrease of wage-earning power; (c) in the case of accidents which have had the same effect.In Bavaria the existing system of income tax came into force on the 1st of January 1900. The rate on earned income varies according to a scale laid down in article 5 of the law, beginning at .1% for incomes up to Â£37, 10s. (1s.), being .66% (Â£2, 5s.) for incomes between Â£230 and Â£250; 1.03% (Â£4) for incomes between Â£350 and Â£375; 1.30% (Â£6, 16s.) for incomes between Â£475 and Â£500 and 1.38% (Â£10) for incomes between Â£650 and Â£700. Incomes exceeding Â£700 and not exceeding Â£1100 pay Â£1 on every Â£50; those between Â£1100 and Â£1700, Â£1, 10s., on every Â£50, between Â£1700 and Â£2050, Â£2 on every Â£50; between Â£2050 and Â£2500, Â£2, 10s. on every Â£50 and beyond Â£2500, 3% on every Â£50. Exemptions from earned income tax are similar to those already mentioned in the case of Prussia. Special abatement in the case of incomes not exceeding Â£250 from all sources is given in consideration of education of children, protracted illness, maintenance of poor relations, serious accidents, &c. The tax on unearned income is at the rate of 1Â½% on incomes from Â£3, 10s. to Â£5; from Â£6 to Â£20, 2%; from Â£21 to Â£35, 2Â½%; from Â£36 to Â£59, 3%; from Â£51 to Â£150, 3Â½%; from Â£151 to Â£5000, 3Â¾%, and over Â£5000, 4%. There is a differentiation in assessment on fluctuating and fixed incomes. Fluctuating incomes (e.g.those derived from literary, scientific or artistic work) are assessed at the average receipts of the two past years. Fixed income is returned at the actual amount at the time of assessment, and the assessment for earned income, both fixed and fluctuating, takes place every four years. Income tax is not levied at the source, but on a direct return by the taxpayer. In the case of unearned income, where a personâ€™s yearly unearned income does not exceed Â£100 and he has no other or only an insignificant additional income, he is required to pay only half the assessed tax. Also in the case where a total income, earned and unearned, does not exceed Â£250 it may, by claiming abatement on such grounds as the education of children, maintenance of indigent relations, &c., be assessed at the lowest rate but one, or be entirely exempt.In WÃ¼rttemberg the General Income Tax Act came into force on the 1st of April 1905. Article 18 provides a graduated scale of rates on incomes from Â£25 upwards. Abatements are allowed for the education and support of children, support of indigent relatives, active service in the army and navy, protracted illness and severe accidents or reverses. There is a supplementary tax of 2% on unearned income from certain kinds of property, such as interest or other income derived from invested capital, dividends, &c., from joint-stock companies and annuities of all kinds. The income tax is not levied at the source, but on a direct return by the ratepayers; assessments are made on the current year, except in the case of fluctuating incomes, when they are made on the income of the preceding year.Hungary.â€”There is no income tax in Hungary at all corresponding to that of the United Kingdom, although proposals for such a tax have from time to time been made.Italy.â€”Graduated income tax in Italy dates from 1864. Incomes are classified according to their characters, and the rate of the tax varies accordingly. In class AÂ¹ are placed incomes derived from interests on capital, and perpetual revenues owned by the state, interests and premiums on communal and provincial loans, dividends of shares issued by companies guaranteed or subsidized by the state lottery prizes. These incomes are assessed at their integral value and pay the full tax of 20%. In class AÂ² are placed incomes derived from capital alone and all perpetual revenues. The assessments on these are reduced to 30/40ths of the actual income and taxed at a rate of 15%. In class B are incomes derived from the co-operation of labour and capital,i.e.those produced by industries and commerce. The assessments of these are reduced to 20/40ths and taxed at 10%. In class C are placed incomes derived from labour alone (private employment) and those represented by temporary revenues or life annuities. Assessments on these are reduced to 18/40ths and taxed at a rate of 9%. In class D are placed incomes from salaries, pensions and all personal allowances made by the state, the provinces and communes. Assessments on these are reduced to 15/40ths and taxed at 7Â½%. Certain abatements are allowed on small incomes in classes B, C and D. Incomes are assessed (1) on the average of the two preceding years in the case of private industries, professions or companies in which liability is unlimited; (b) on the income of the current year in the case of incomes from dividends, salaries, pensions and fixed allowances, as well as in the case of incomes of communes, provinces and corporations; (c) on the basis of the account closed before the previous July of the current year in the case of incomes of limited liability companies, banks and savings banks.Netherlands.â€”In the Netherlands there is a property tax imposed upon income derived from capital, as well as a tax on income earned by labour.Norway.â€”In Norway under the state income tax incomes under 1000 kroner are exempt, those between 1000 and 4000 kroner pay 2% on that part liable to taxation; those between 4000 and 7000 kroner pay 3%; those between 7000 and 10,000 kroner pay 4%, and those above 10,000 kroner 5%. Persons liable to taxation are divided into (a) those who have no one to support, as companies and the like; (b) those who have from one to three persons to support; (c) those who have from four to six persons to support; (d) those who have seven or more persons to support. Those who are counted as dependent upon the taxpayer are his children, own or adopted, his parents, brothers and sisters, and other relations and connexions by marriage who might have a reasonable claim to his support. A certain part of the income liable to taxation is abated by a graduated scale according to the class into which the ratepayer falls.Spain.â€”In Spain the income tax is divided into (a) that derived from personal exertion and (b) that derived from property. Directors, managers and representatives of banks, companies and societies pay 10%; those employed in banks, &c., commercial houses, and those in private employment, as well as actors, bullfighters, professional pelota-players, acrobats, conjurers, &c., pay 5%. Those employed by the day or those whose salary is under Â£45 are exempt, as are also masters in primary schools. Income derived from property is taxed according to the source from which the income is derived,e.g.income from shares in public works is rated at 20%, income from shares in ordinary companies, railways, tramways or canals at 3%, from dividends on bank shares at 5%, from mining shares at only 2%. There is also an industry tax,i.e.on the exercise of industrial, commercial and professional enterprises, which tax is divided into five different tariffs, of which I. applies to commerce (vendors), II. also to commerce (middlemen), III. to industry (machinery), IV. to professions and V. to licences (retail and itinerant vendors). Tariff I. is differentiated according to the importance of the business and of the locality in which it is carried on, the rate being fixed by a consideration of the two combined. Tariff II. is differentiated according to the character of the enterprise, its importance and the importance of the locality. Tariff III. is differentiated according to either motive power, output, method, product or locality; Tariff IV. according to the character of the profession and the importance of the locality; Tariff V. is also differentiated according to the locality and the importance of the business.Switzerland.â€”The system of income tax varies in the different cantons. Broadly speaking, these may be divided into four different kinds: (1) a graduated property tax, in which the rate applicable to each class of fortune is definitely fixed; (2) a proportional tax, under which property and income are chargeable, each at a fixed rate, while the total amount of the tax is liable to a proportionate increase according to scale if it exceeds certain specified amounts; (3) a system by which property and income are divided into three classes, the rate of the tax being increased by a graduated rise, according to the class to which the property or income belongs, and (4) a uniform rate of tax, with progression in the amount of income liable to taxation.United States.â€”One of the means adopted by the Federal Government for meeting its expenses during the Civil War was the levying of an income tax. By the Act of Congress of the 5th of August 1861 a tax of 3% was imposed on all incomes, with an exemption of $800, and was made payable on or before the 30th of June 1862. No tax, however, was assessed under the law. In March 1862 a new income tax bill was introduced into the House of Representatives. This act, which was signed on the 1st of July 1862, imposed a tax of 3% on all incomes not over $10,000, and 5% on all incomes above that sum, with an exemption of $600. It was also provided that dividends of banks, insurance companies and railways should be assessed directly; but the bond-holder was allowed to deduct the dividend so assessed from his taxable income. In the case of government salaries, the tax was deducted before the salaries were paid. The income tax was first levied in 1863. The rate was changed by act of Congress in 1865, 1867 and 1870, and a joint resolution in 1864 imposed a special additional tax of 5% for that year. The tax was finally abolished in 1872. The total amount produced by the tax from the beginning was $376,150,209. The constitutionality of the act was subsequently brought into question, but was upheld by a unanimous decision of the Supreme Court in 1880, which held that the tax was not a direct tax but an excise tax, and that Congress had a right to impose it so long as it was made uniform throughout the United States. On the 27th of August 1894 an income tax act was passed as part of the Wilson Bill. By this act it was provided that a tax of2% on all incomes should be levied from the 1st of January 1895 to the 1st of January 1900, with an exemption of $4000. The legality of the tax was assailed, chiefly on the ground that it was a direct tax, and not apportioned among the several states in proportion to their population. On the 20th of May 1895 the Supreme Court, by a vote of five to four, declared the tax to be unconstitutional. Accordingly, before any federal income tax could be imposed, there was needed an amendment of the constitution, and a movement in this direction gradually began. In the first year of the presidency of Mr W. H. Taft both Houses of Congress passed by the necessary two-thirds majority a resolution to submit the proposal to the 46 states, the wording of the amendment being â€œThat Congress shall have power to lay and collect taxes on incomes from whatever source derived, without apportionment among the several States, and without regard to any census enumeration.â€Cape Colony.â€”Cape Colony was the only South African colony which, prior to the Union in 1910, had a system of income tax, which was first imposed by an act of the 31st of May 1904. Incomes not exceeding Â£1000 per annum were exempt from taxation; incomes exceeding Â£1000 but not exceeding Â£2000 were taxed 6d. in the pound on the excess beyond Â£1000; those between Â£2000 and Â£5000 were exempt for the first Â£1000, paid 6d. in the pound on the next Â£1000 and 9d. in the pound on the remainder; those exceeding Â£5000 paid 6d. in the pound on the second Â£1000, 9d. in the pound on the next Â£3000 and 1s. in the pound on the remainder.New South Wales.â€”Income tax in New South Wales first came into operation on the 1st of January 1896. It is complementary with a land tax, assessed on the unimproved value of freehold lands (with certain exemptions and deductions). Incomes of Â£200 per annum and under are exempt, and all other incomes (except those of companies) are entitled to a reduction of Â£200 in their assessments. The rate of tax is 6d. in the pound. There are certain incomes, revenues and funds which are exempt from taxation, such as those of municipal corporations or other local authorities, of mutual life insurance societies and of other companies or societies not carrying on business for purposes of profit or gain, and of educational, ecclesiastical and charitable institutions of a public character, &c.New Zealand.â€”In New Zealand the income tax is also complementary with a land tax. Incomes up to Â£300 per annum are exempt; incomes up to Â£1000 per annum are taxed 6d. in the pound, with an exemption of Â£300 and life insurance premiums up to Â£50; incomes over Â£1300 pay 1s. in the pound, which is also the tax on the income of trading companies, to whom no exemption is allowed. The income of friendly societies, savings banks, co-operative dairy companies, public societies not carrying on business for profit, &c., are exempt from income tax.Queensland.â€”In Queensland income tax is levied on (a) income derived from property such as rents, interest, income from companies, royalties, &c., and (b) on income derived from personal exertion. On income derived from property all incomes not exceeding Â£100 are exempt; incomes between Â£100 and Â£120 pay Â£1 tax; those over Â£120 but under Â£300 have Â£100 exempt and pay 1s. in each and every pound over Â£100, while incomes over Â£300 pay 1s. in each and every pound. Incomes from personal exertion pay 10s. between Â£100 and Â£125; Â£1 between Â£126 and Â£150; between Â£151 and Â£300 have Â£100 exempt and pay 6d. in each and every pound over Â£100: between Â£301 and Â£500 6d. in every pound; between Â£501 and Â£1000 6d. in every pound of the first Â£500 and 7d. in every pound over Â£500, between Â£1001 and Â£1500 7d. in every pound of the first Â£1000, and 8d. in every pound over Â£1000; incomes over Â£1500 pay 8d. in every pound; 1s. in every pound is charged on the incomes of all companies and of all absentees.South Australia.â€”The income tax dates from 1884 and is levied on all incomes arising, accruing in or derived from South Australia, except municipal corporations, district councils, societies, &c., not carrying on business for the purpose ot gain, and all friendly societies. Where the income is derived from personal exertion the rate of tax is 4Â½d. in the pound up to Â£800, and 7d. in the pound over Â£800. For income derived from property the rate is 9d. in the pound up to Â£800, and 1s. 1Â½d. in the pound over Â£800. There is an exemption of Â£150 on incomes up to Â£400, but no exemption over that limit.Tasmania.â€”In Tasmania there is (a) an income tax proper, and (b) a non-inquisitorial ability tax, one complementary to the other. The income tax proper is levied on all income of any company, at the rate of 1s. for every pound of the taxable amount; on all income of any person, at the rate of 1s. for every pound of the taxable amount derived from property, and on every dividend at the same rate. Personal incomes of Â£400 and over are assessed at the full amount, but an abatement of Â£10 for every Â£50 of income is allowed on incomes below Â£400 down to incomes of Â£150, which thus have Â£50 deducted; incomes between Â£120 and Â£150 have Â£60 deducted; incomes between Â£110 and Â£120, Â£70, and incomes between Â£100 and Â£110, Â£80. The ability tax is paid by (a) occupiers and sub-occupiers of property and (b) by lodgers. The amount of tax paid by occupiers or sub-occupiers is calculated upon the assessed annual value of the property occupied, and that of lodgers from the assessed annual value of their board and lodging. A detailed account of both taxes will be found in House of Commons Papers, No. 282 of 1905.Victoria.â€”In Victoria the rate of income tax is fixed annually by act. The rate charged on income derived from property is exactly double that charged on income derived from personal exertion, the rate for which for 1905 was: on the first Â£500 or fractional part thereof, 3d. in the pound; on the second Â£500 or fractional part thereof, 4d. in the pound; on the third Â£500 or fractional part thereof, 5d. in the pound; on all incomes in excess of Â£1500, 6d. in the pound. All companies, except life insurance companies, were charged 7d. in the pound on their incomes; life insurance companies were charged 8d. in the pound.Bibliography.â€”The Annual Reports of the Commissioners of Inland Revenue, the Reports of Committees and other references mentioned in the article, as well as Dowellâ€™sHistory of Taxation in England(1884); Dowellâ€™sActs relating to the Income Tax(6th ed., 1908), and Robinsonâ€™sLaw relating to Income Tax(2nd ed., 1908).

Belgium.â€”No income tax proper exists in Belgium, but there is a state tax of 2% on the dividends of joint stock companies.

Denmark.â€”Income tax is levied under a law of the 15th of May 1903. Incomes under 2000 kroner pay a tax of 1.3%; under 3000 kroner, 1.4%; under 4000 kroner, 1.5%; under 6000 kroner, 1.6%; under 8000 kroner, 1.7%; under 10,000 kroner, 1.8%; under 15,000 kroner, 1.9%; under 20,000 kroner, 2.0% and for every additional 10,000 kroner up to 100,000 kroner 1%, incomes of 100,000 kroner and upwards paying 2.5%. Exempt from the duty areâ€”the king, members of the royal family and the civil list; the legations, staffs and consular officers of foreign powers (not being Danish subjects); foreigners temporarily resident in the country; mortgage societies, credit institutions, savings and loan banks. The increase in capital resulting from an increase in value of properties is not deemed incomeâ€”on the other hand no deduction in income is made if such properties decrease in valueâ€”nor are daily payments and travelling expenses received for the transaction of business on public service, if the person has thereby been obliged to reside outside his own parish. Certain deductions can be made in calculating incomeâ€”such as working expenses, office expenses, pensions and other burthens, amounts paid for direct taxation, dues to commune and church, tithe, tenant and farming charges, heirsâ€™ allowances and similar burthens; interest on mortgages and other debts, and what has been spent for necessary maintenance or insurance of the property of the taxpayer. There are also certain exemptions with respect to companies not having an establishment in the country.

France.â€”There is no income tax in France corresponding exactly to that levied in the United Kingdom. There are certain direct taxes, such as the taxes on buildings,personnelle mobiliÃ¨re, and doors and windows (impÃ´ts de rÃ©partition)â€”the tax levied on income from land and from all trades and professions (impÃ´ts de quotitÃ©) which bear a certain resemblance to portions of the British income tax (seeFrance:Finance). From time to time a graduated income tax has been under discussion in the French Chambers, the proposal being to substitute such a tax for the existing (personnelle mobiliÃ¨re) and doors and windows taxes, but no agreement on the matter has been reached.

German Empire.â€”In Prussia the income tax is levied under a law of the 24th of June 1891. All persons with incomes of over Â£150 per annum are required to send in an annual declaration of their full income, divided according to four main sourcesâ€”(a) capital; (b) landed property; (c) trade and industry; (d) employment bringing gain, this latter including the salary or wages of workmen, servants and industrial assistants, military persons and officials; also the receipts of authors, artists, scientists, teachers and tutors. Liability for income tax, however, begins with an income of Â£45, and rises by a regular system of progression, the rate being about 3% of the income. Thus an income of more than Â£45, but under Â£52, 10s. pays a tax of 6s. and so on up to Â£475, an income over that sum but under Â£525 paying a tax of 15s. Incomes over Â£525 rise by steps of Â£50 up to Â£1525, for every step Â£1, 10s. being paid. Incomes between Â£1526 and Â£1600 rise by steps of Â£75, Â£3 being paid for every step. Between Â£1601 and Â£3900, the steps are Â£100, and the tax Â£4 a step; from Â£3901 to Â£5000 the steps are the same (Â£100), but the tax is Â£5 a step. There is also a supplementary tax on property of about1â„20th% of the assessed value. This supplementary tax is not levied on those whose taxable property does not exceed a total value of Â£300, nor on those whose annual income does not exceed Â£45, if the total value of their taxable property does not exceed Â£1000, nor on women who have members of their own family under age to maintain, nor on orphans under age, nor on persons incapable of earning incomes if their taxable property does not exceed Â£1000 nor their income Â£60. There are a number of exemptions from the income tax, some of the more important beingâ€”(a) the military incomes of non-commissioned officers and privates, also of all persons on the active list of the army or navy as long as they belong to a unit in war formation; (b) extraordinary receipts from inheritances, presents, insurances, from the sale of real estate not undertaken for purposes of industry or speculation, and similar profits (all of which are reckoned as increases of capital); (c) expenses incurred for the purpose of acquiring, assuring and maintaining income; (d) interest on debts; (e) the regular annual depreciation arising from wear of buildings, machines, tools, &c., in so far as they are not included under working expenses; (f) the contributions which taxpayers are compelled by law or agreement to pay to invalid, accident, old age insurance, widow, orphan and pension funds; (g) insurance premiums. Moreover, persons liable to taxation with an income of not more than Â£150 may deduct from that income Â£2, 10s. for every member of their family under fourteen years of age, and abatement is also allowed to persons with incomes up to Â£475 whose solvency has been unfavourably affected by adverse economic circumstances. The income tax is both levied at the source (as in the case of companies) and assessed on a direct return by the taxpayer of his income from all sources. Salaries are not taxed before payment. Fixed receipts are assessed according to their amount for the taxation year in which the assessment is made, and variable incomes on anaverage of the three years immediately preceding the assessment. The income tax and the supplementary tax are collected in the first half of the second month of each quarter by the communities (Gemeinden) who bear the whole cost.

In Saxony a graduated tax is in force on all incomes of Â£20 per annum and upwards. All corporate bodies and individuals who derive their income or any portion of it from Saxony are liable to the extent of that income, except those serving religious, charitable or public purposes. Incomes between Â£20 and Â£5000 are divided into 118 classes, in which the rate rises progressively. From Â£500 to Â£5000 the classes rise by Â£50, and above Â£5000 by Â£100. The rate of income tax begins at Â¼%,i.e.1s. on an income of Â£20. An abatement is allowed to those whose incomes do not exceed Â£155 of Â£2, 10s. for each child between the ages of six and fourteen years, provided such abatements do not reduce the income by more than one class. In the case of persons with incomes not exceeding Â£290 abatement (not exceeding three classes) is allowedâ€”(a) when the support of children or indigent relations involves a burden of such a nature as to affect the general standard of living; (b) on account of long-continued illness, involving heavy expense; and, on restoration to health, temporary decrease of wage-earning power; (c) in the case of accidents which have had the same effect.

In Bavaria the existing system of income tax came into force on the 1st of January 1900. The rate on earned income varies according to a scale laid down in article 5 of the law, beginning at .1% for incomes up to Â£37, 10s. (1s.), being .66% (Â£2, 5s.) for incomes between Â£230 and Â£250; 1.03% (Â£4) for incomes between Â£350 and Â£375; 1.30% (Â£6, 16s.) for incomes between Â£475 and Â£500 and 1.38% (Â£10) for incomes between Â£650 and Â£700. Incomes exceeding Â£700 and not exceeding Â£1100 pay Â£1 on every Â£50; those between Â£1100 and Â£1700, Â£1, 10s., on every Â£50, between Â£1700 and Â£2050, Â£2 on every Â£50; between Â£2050 and Â£2500, Â£2, 10s. on every Â£50 and beyond Â£2500, 3% on every Â£50. Exemptions from earned income tax are similar to those already mentioned in the case of Prussia. Special abatement in the case of incomes not exceeding Â£250 from all sources is given in consideration of education of children, protracted illness, maintenance of poor relations, serious accidents, &c. The tax on unearned income is at the rate of 1Â½% on incomes from Â£3, 10s. to Â£5; from Â£6 to Â£20, 2%; from Â£21 to Â£35, 2Â½%; from Â£36 to Â£59, 3%; from Â£51 to Â£150, 3Â½%; from Â£151 to Â£5000, 3Â¾%, and over Â£5000, 4%. There is a differentiation in assessment on fluctuating and fixed incomes. Fluctuating incomes (e.g.those derived from literary, scientific or artistic work) are assessed at the average receipts of the two past years. Fixed income is returned at the actual amount at the time of assessment, and the assessment for earned income, both fixed and fluctuating, takes place every four years. Income tax is not levied at the source, but on a direct return by the taxpayer. In the case of unearned income, where a personâ€™s yearly unearned income does not exceed Â£100 and he has no other or only an insignificant additional income, he is required to pay only half the assessed tax. Also in the case where a total income, earned and unearned, does not exceed Â£250 it may, by claiming abatement on such grounds as the education of children, maintenance of indigent relations, &c., be assessed at the lowest rate but one, or be entirely exempt.

In WÃ¼rttemberg the General Income Tax Act came into force on the 1st of April 1905. Article 18 provides a graduated scale of rates on incomes from Â£25 upwards. Abatements are allowed for the education and support of children, support of indigent relatives, active service in the army and navy, protracted illness and severe accidents or reverses. There is a supplementary tax of 2% on unearned income from certain kinds of property, such as interest or other income derived from invested capital, dividends, &c., from joint-stock companies and annuities of all kinds. The income tax is not levied at the source, but on a direct return by the ratepayers; assessments are made on the current year, except in the case of fluctuating incomes, when they are made on the income of the preceding year.

Hungary.â€”There is no income tax in Hungary at all corresponding to that of the United Kingdom, although proposals for such a tax have from time to time been made.

Italy.â€”Graduated income tax in Italy dates from 1864. Incomes are classified according to their characters, and the rate of the tax varies accordingly. In class AÂ¹ are placed incomes derived from interests on capital, and perpetual revenues owned by the state, interests and premiums on communal and provincial loans, dividends of shares issued by companies guaranteed or subsidized by the state lottery prizes. These incomes are assessed at their integral value and pay the full tax of 20%. In class AÂ² are placed incomes derived from capital alone and all perpetual revenues. The assessments on these are reduced to 30/40ths of the actual income and taxed at a rate of 15%. In class B are incomes derived from the co-operation of labour and capital,i.e.those produced by industries and commerce. The assessments of these are reduced to 20/40ths and taxed at 10%. In class C are placed incomes derived from labour alone (private employment) and those represented by temporary revenues or life annuities. Assessments on these are reduced to 18/40ths and taxed at a rate of 9%. In class D are placed incomes from salaries, pensions and all personal allowances made by the state, the provinces and communes. Assessments on these are reduced to 15/40ths and taxed at 7Â½%. Certain abatements are allowed on small incomes in classes B, C and D. Incomes are assessed (1) on the average of the two preceding years in the case of private industries, professions or companies in which liability is unlimited; (b) on the income of the current year in the case of incomes from dividends, salaries, pensions and fixed allowances, as well as in the case of incomes of communes, provinces and corporations; (c) on the basis of the account closed before the previous July of the current year in the case of incomes of limited liability companies, banks and savings banks.

Netherlands.â€”In the Netherlands there is a property tax imposed upon income derived from capital, as well as a tax on income earned by labour.

Norway.â€”In Norway under the state income tax incomes under 1000 kroner are exempt, those between 1000 and 4000 kroner pay 2% on that part liable to taxation; those between 4000 and 7000 kroner pay 3%; those between 7000 and 10,000 kroner pay 4%, and those above 10,000 kroner 5%. Persons liable to taxation are divided into (a) those who have no one to support, as companies and the like; (b) those who have from one to three persons to support; (c) those who have from four to six persons to support; (d) those who have seven or more persons to support. Those who are counted as dependent upon the taxpayer are his children, own or adopted, his parents, brothers and sisters, and other relations and connexions by marriage who might have a reasonable claim to his support. A certain part of the income liable to taxation is abated by a graduated scale according to the class into which the ratepayer falls.

Spain.â€”In Spain the income tax is divided into (a) that derived from personal exertion and (b) that derived from property. Directors, managers and representatives of banks, companies and societies pay 10%; those employed in banks, &c., commercial houses, and those in private employment, as well as actors, bullfighters, professional pelota-players, acrobats, conjurers, &c., pay 5%. Those employed by the day or those whose salary is under Â£45 are exempt, as are also masters in primary schools. Income derived from property is taxed according to the source from which the income is derived,e.g.income from shares in public works is rated at 20%, income from shares in ordinary companies, railways, tramways or canals at 3%, from dividends on bank shares at 5%, from mining shares at only 2%. There is also an industry tax,i.e.on the exercise of industrial, commercial and professional enterprises, which tax is divided into five different tariffs, of which I. applies to commerce (vendors), II. also to commerce (middlemen), III. to industry (machinery), IV. to professions and V. to licences (retail and itinerant vendors). Tariff I. is differentiated according to the importance of the business and of the locality in which it is carried on, the rate being fixed by a consideration of the two combined. Tariff II. is differentiated according to the character of the enterprise, its importance and the importance of the locality. Tariff III. is differentiated according to either motive power, output, method, product or locality; Tariff IV. according to the character of the profession and the importance of the locality; Tariff V. is also differentiated according to the locality and the importance of the business.

Switzerland.â€”The system of income tax varies in the different cantons. Broadly speaking, these may be divided into four different kinds: (1) a graduated property tax, in which the rate applicable to each class of fortune is definitely fixed; (2) a proportional tax, under which property and income are chargeable, each at a fixed rate, while the total amount of the tax is liable to a proportionate increase according to scale if it exceeds certain specified amounts; (3) a system by which property and income are divided into three classes, the rate of the tax being increased by a graduated rise, according to the class to which the property or income belongs, and (4) a uniform rate of tax, with progression in the amount of income liable to taxation.

United States.â€”One of the means adopted by the Federal Government for meeting its expenses during the Civil War was the levying of an income tax. By the Act of Congress of the 5th of August 1861 a tax of 3% was imposed on all incomes, with an exemption of $800, and was made payable on or before the 30th of June 1862. No tax, however, was assessed under the law. In March 1862 a new income tax bill was introduced into the House of Representatives. This act, which was signed on the 1st of July 1862, imposed a tax of 3% on all incomes not over $10,000, and 5% on all incomes above that sum, with an exemption of $600. It was also provided that dividends of banks, insurance companies and railways should be assessed directly; but the bond-holder was allowed to deduct the dividend so assessed from his taxable income. In the case of government salaries, the tax was deducted before the salaries were paid. The income tax was first levied in 1863. The rate was changed by act of Congress in 1865, 1867 and 1870, and a joint resolution in 1864 imposed a special additional tax of 5% for that year. The tax was finally abolished in 1872. The total amount produced by the tax from the beginning was $376,150,209. The constitutionality of the act was subsequently brought into question, but was upheld by a unanimous decision of the Supreme Court in 1880, which held that the tax was not a direct tax but an excise tax, and that Congress had a right to impose it so long as it was made uniform throughout the United States. On the 27th of August 1894 an income tax act was passed as part of the Wilson Bill. By this act it was provided that a tax of2% on all incomes should be levied from the 1st of January 1895 to the 1st of January 1900, with an exemption of $4000. The legality of the tax was assailed, chiefly on the ground that it was a direct tax, and not apportioned among the several states in proportion to their population. On the 20th of May 1895 the Supreme Court, by a vote of five to four, declared the tax to be unconstitutional. Accordingly, before any federal income tax could be imposed, there was needed an amendment of the constitution, and a movement in this direction gradually began. In the first year of the presidency of Mr W. H. Taft both Houses of Congress passed by the necessary two-thirds majority a resolution to submit the proposal to the 46 states, the wording of the amendment being â€œThat Congress shall have power to lay and collect taxes on incomes from whatever source derived, without apportionment among the several States, and without regard to any census enumeration.â€

Cape Colony.â€”Cape Colony was the only South African colony which, prior to the Union in 1910, had a system of income tax, which was first imposed by an act of the 31st of May 1904. Incomes not exceeding Â£1000 per annum were exempt from taxation; incomes exceeding Â£1000 but not exceeding Â£2000 were taxed 6d. in the pound on the excess beyond Â£1000; those between Â£2000 and Â£5000 were exempt for the first Â£1000, paid 6d. in the pound on the next Â£1000 and 9d. in the pound on the remainder; those exceeding Â£5000 paid 6d. in the pound on the second Â£1000, 9d. in the pound on the next Â£3000 and 1s. in the pound on the remainder.

New South Wales.â€”Income tax in New South Wales first came into operation on the 1st of January 1896. It is complementary with a land tax, assessed on the unimproved value of freehold lands (with certain exemptions and deductions). Incomes of Â£200 per annum and under are exempt, and all other incomes (except those of companies) are entitled to a reduction of Â£200 in their assessments. The rate of tax is 6d. in the pound. There are certain incomes, revenues and funds which are exempt from taxation, such as those of municipal corporations or other local authorities, of mutual life insurance societies and of other companies or societies not carrying on business for purposes of profit or gain, and of educational, ecclesiastical and charitable institutions of a public character, &c.

New Zealand.â€”In New Zealand the income tax is also complementary with a land tax. Incomes up to Â£300 per annum are exempt; incomes up to Â£1000 per annum are taxed 6d. in the pound, with an exemption of Â£300 and life insurance premiums up to Â£50; incomes over Â£1300 pay 1s. in the pound, which is also the tax on the income of trading companies, to whom no exemption is allowed. The income of friendly societies, savings banks, co-operative dairy companies, public societies not carrying on business for profit, &c., are exempt from income tax.

Queensland.â€”In Queensland income tax is levied on (a) income derived from property such as rents, interest, income from companies, royalties, &c., and (b) on income derived from personal exertion. On income derived from property all incomes not exceeding Â£100 are exempt; incomes between Â£100 and Â£120 pay Â£1 tax; those over Â£120 but under Â£300 have Â£100 exempt and pay 1s. in each and every pound over Â£100, while incomes over Â£300 pay 1s. in each and every pound. Incomes from personal exertion pay 10s. between Â£100 and Â£125; Â£1 between Â£126 and Â£150; between Â£151 and Â£300 have Â£100 exempt and pay 6d. in each and every pound over Â£100: between Â£301 and Â£500 6d. in every pound; between Â£501 and Â£1000 6d. in every pound of the first Â£500 and 7d. in every pound over Â£500, between Â£1001 and Â£1500 7d. in every pound of the first Â£1000, and 8d. in every pound over Â£1000; incomes over Â£1500 pay 8d. in every pound; 1s. in every pound is charged on the incomes of all companies and of all absentees.

South Australia.â€”The income tax dates from 1884 and is levied on all incomes arising, accruing in or derived from South Australia, except municipal corporations, district councils, societies, &c., not carrying on business for the purpose ot gain, and all friendly societies. Where the income is derived from personal exertion the rate of tax is 4Â½d. in the pound up to Â£800, and 7d. in the pound over Â£800. For income derived from property the rate is 9d. in the pound up to Â£800, and 1s. 1Â½d. in the pound over Â£800. There is an exemption of Â£150 on incomes up to Â£400, but no exemption over that limit.

Tasmania.â€”In Tasmania there is (a) an income tax proper, and (b) a non-inquisitorial ability tax, one complementary to the other. The income tax proper is levied on all income of any company, at the rate of 1s. for every pound of the taxable amount; on all income of any person, at the rate of 1s. for every pound of the taxable amount derived from property, and on every dividend at the same rate. Personal incomes of Â£400 and over are assessed at the full amount, but an abatement of Â£10 for every Â£50 of income is allowed on incomes below Â£400 down to incomes of Â£150, which thus have Â£50 deducted; incomes between Â£120 and Â£150 have Â£60 deducted; incomes between Â£110 and Â£120, Â£70, and incomes between Â£100 and Â£110, Â£80. The ability tax is paid by (a) occupiers and sub-occupiers of property and (b) by lodgers. The amount of tax paid by occupiers or sub-occupiers is calculated upon the assessed annual value of the property occupied, and that of lodgers from the assessed annual value of their board and lodging. A detailed account of both taxes will be found in House of Commons Papers, No. 282 of 1905.

Victoria.â€”In Victoria the rate of income tax is fixed annually by act. The rate charged on income derived from property is exactly double that charged on income derived from personal exertion, the rate for which for 1905 was: on the first Â£500 or fractional part thereof, 3d. in the pound; on the second Â£500 or fractional part thereof, 4d. in the pound; on the third Â£500 or fractional part thereof, 5d. in the pound; on all incomes in excess of Â£1500, 6d. in the pound. All companies, except life insurance companies, were charged 7d. in the pound on their incomes; life insurance companies were charged 8d. in the pound.

Bibliography.â€”The Annual Reports of the Commissioners of Inland Revenue, the Reports of Committees and other references mentioned in the article, as well as Dowellâ€™sHistory of Taxation in England(1884); Dowellâ€™sActs relating to the Income Tax(6th ed., 1908), and Robinsonâ€™sLaw relating to Income Tax(2nd ed., 1908).

1Full statistics of the yield of income tax and other information pertaining thereto will be found in theReports of the Commissioners of His Majestyâ€™s Inland Revenue(published annually); those issued in 1870 and in 1885 are especially interesting.2In Appendix No. 4 to theReport from the Select Committee on Income Tax(1906), will be found a valuable list (prepared in the Library of the London School of Economics) of references to the graduation of the income tax and the distribution of incomes both in the United Kingdom and in other countries.

2In Appendix No. 4 to theReport from the Select Committee on Income Tax(1906), will be found a valuable list (prepared in the Library of the London School of Economics) of references to the graduation of the income tax and the distribution of incomes both in the United Kingdom and in other countries.

INCORPORATION(from Lat.incorporare, to form into a body), in law, the embodying or formation of a legal corporation, brought about either by a general rule contained in such laws,e.g.as the Companies acts, and applicable wherever its conditions are satisfied; or by a special act of sovereign power,e.g.an incorporating statute or charter. The word is used also in the sense of uniting,e.g.a will may incorporate by reference other papers, which may be then taken as part of the will, as much as if they were set out at length in it.

INCUBATIONandINCUBATORS. The subject of â€œincubationâ€ (Lat.incubare, to brood;in-cumbere, to lie on), a term which, while strictly signifying the action of a hen in sitting on her eggs to hatch them, is also used in pathology for the development within the body of the germs of disease, is especially associated with the artificial means, or â€œincubators,â€ devised for hatching eggs, or for analogous purposes of an artificial foster-mother nature, or for use in bacteriological laboratories.

Life is dependent, alike for its awakening and its maintenance, upon the influence of certain physical and chemical factors, among which heat and moisture may be regarded as the chief. It is therefore obvious that any method of incubation must provide for a due degree of temperature and moisture. And this degree must be one within limits, for while all organisms are plastic and can attune themselves to a greater or less range of variation in their physical environment, there is a given degree at which the processes of life in each species proceed most favourably. It is this particular degree, which differs for different species, which must be attained, if artificial incubation is to be successfully conducted. In other words, the degree of temperature and moisture within the incubation drawer must remain uniform throughout the period of incubation if the best results are to be reached. It is not easy to attain these conditions, for there are many disturbing factors. We may therefore next consider the more important of them.

The chief causes which operate to make the temperature within the incubator drawer variable are the changes of the temperature of the outer air, fluctuations in the pressure of the gas when that is used as the source of heat, or the gradual diminution of the oxidizing power of the flame and wick when an oil lamp is substituted for gas. Also, the necessary opening of the incubator drawer, either for airing or for sprinkling the eggs with water when that is necessary, tends to reduce the temperature. But there is another equally important though less obvious source of disturbance, and this resides within the organism undergoing incubation. In the case of the chick, at about the ninth or tenth days of incubation important changes are occurring. Between this period and the fourteenth day the chick becomes relatively large and bulky, and the temporary respiratory organ, the allantois, together with its veins, increases greatly in size and extent. As a consequence, the respiratory processes are enabled to proceed with greater activity, and the chemical processes of oxidation thus enhanced necessarily largely increase the amount of heat which the chick itself produces. Thus an incubator, to be successful, must be capable of automatically adjusting itself to this heightened temperature.

The drawer of an incubator is a confined space and is usually packed as closely as possible with the contained eggs. The eggs are living structures and consequently need air. This necessitates some method of direct ventilation, and this in its turn necessarily increases the evaporation of water vapour from the surface of the egg. Unless, therefore, this evaporation is checked, the eggs will be too dry at the periodâ€”from the tenth day onwardsâ€”whenmoisture is more than ever an important factor. There is, according to some poultry authorities, reason to believe that the sitting hen secretes some oily substance which, becoming diffused over the surface of the egg, prevents or retards evaporation from within; presumably, this oil is permeable to oxygen. In nature, with the sitting hen, and in the â€œMamalâ€ artificial incubating establishments of the Egyptians, direct air currents do not exist, owing to the large size of the chambers, and consequently incubation can be successfully achieved without any special provision for the supply of moisture.

Artificial incubation has been known to the Egyptians and the Chinese from almost time immemorial. In Egypt, at Berme on the Delta, the trade of artificial hatching is traditionally transmitted from father to son, and is consequently confined to particular families. The secrets of the process are guarded with a religious zeal, and the individuals who practise it are held under plighted word not to divulge them. It is highly probable that the process of artificial incubation as practised by the Egyptians is not so simple as it is believed to be. But as far as the structures and processes involved have been ascertained by travellers, it appears that the â€œMamalâ€ is a brick building, consisting of four large ovens, each of such a size that several men could be contained within it. These ovens are in pairs, in each pair one oven being above the other, on each side of a long passage, into which they open by a circular aperture, just large enough for a man to obtain access to each. The eggs are placed in the middle of the floor of the oven, and in the gutters round the sides the fire is lighted. The material for this latter, according to one account, consists of camelsâ€™ dung and chopped hay, and according to another of horsesâ€™ dung. The attainment of the right degree of heat is apparently reached wholly by the skill of the persons employed. When this has been attained, they plug the entrance hole with coarse tow. On the tenth to twelfth days they cease to light the fires.

Each â€œMamalâ€ may contain from 40,000 to 80,000 eggs. There are 386 â€œMamalsâ€ in the country, which are only worked for six months of the year, and produce in that time eight broods. Many more than two-thirds of the eggs put in are successfully hatched. It is estimated that 90,000,000 eggs are annually hatched by the Bermeans.

A method of incubating that appears to have been altogether overlooked in Englandâ€”or at least never to have been practisedâ€”is that carried on by theCouveursor professional hatchers in France. They make use of hen-turkeys for the purpose, and each bird can be made to sit continuously for from three to six months. Themodus operandiis as follows: a dark room which is kept at a constant temperature throughout the year contains a number of boxes, just large enough to accommodate a turkey. The bottom of the box is filled with some vegetable material, bracken, hay, heather, straw or cocoa-fibres. Each box is covered in with lattice-work wire, so arranged that the freedom of the sitting bird is limited and its escape prevented. Dummy eggs, made by emptying addled ones and filling with plaster of Paris, are then placed in the nest and a bird put in. At first it endeavours to escape, but after an interval of a few days it becomes quiet, and the dummy eggs being then removed, fresh ones are inserted. As soon as the chickens are hatched, they are withdrawn and fresh eggs substituted. The hen turkeys are also used successfully as foster-mothers. Each bird can adequately cover about two dozen eggs.

Incubation as an industry in Europe and America is of recent development. The growing scarcity of game birds of all kinds, coincident with the increase of population, and the introduction of the breech-loading gun, together with the marked revival of interest in fancy poultry about the year 1870, led, however, to the production of a great variety of appliances designed to render artificial incubation successful.

Previously to this, several interesting attempts had been made. As long ago as 1824, Walthew constructed an incubator designed to be used by farmersâ€™ wives with the aid of no more than ordinary household conditions. It consisted of a double-walled metal box, with several pipes opening into the walled space round the sides, bottom and top of the incubator. These pipes were connected with an ordinary kitchen boiler. Walthew, however, constructed a fire grate, with a special boiler adapted to the requirements of the incubator. Into the walled space of the incubator, steam from the kitchen boiler passed; the excess steam escaped from an aperture in the roof, and the condensed steam through one in the floor. Ventilating holes and also plugs, into which thermometers were placed, pierced the door of the incubator.

In 1827, J. H. Barlow successfully reared hens and other birds by means of steam at Drayton Green, Ealing. He constructed very large rooms and rearing houses, expending many thousands of pounds upon the work. He reared some 64,000 game birds annually. The celebrated physician Harvey, and the famous anatomist Hunter were much interested in his results.

To John Champion, Berwick-on-Tweed, in 1870, belongs, however, the credit of instituting a system which, when extended, may become the system of the future, and will rival the ancient â€œMamalsâ€ in the success of the incubation and in the largeness of the numbers of eggs incubated. He used a large room through which passed two heated flues, the eggs being placed upon a table in the centre. The flues opened out into an adjoining space. The temperature of the room was adjusted by personal supervision of the fire. This system, more elaborated and refined, is now in use in some parts of America.

Bird Incubators.

Owing to the great variety in the details of construction, it is difficult to arrange a classification of incubators which shall include them all. They may, however, be classified in one of two ways. We may either consider the method by which they are heated or the method by which their temperature is regulated.

In the former case we may divide them into â€œhot-airâ€ incubators and into â€œhot-waterâ€ or â€œtankâ€ incubators. In the latter ease we may classify them according as their thermostat or temperature-regulator is actuated by a liquid expanding with rising temperature, or by solids, usually metals.

In America incubators of the hot-air type with solid and metallic thermostats are most used, while in Europe the â€œtankâ€ type, with a thermostat of expansible liquid, prevails.

For the purpose of more adequately considering the various forms which have been in use, or are still used, we shall here divide them into the â€œhot-airâ€ and â€œhot-waterâ€ (or â€œtankâ€) classes.

In the hot-air types the incubator chamber is heated by columns of hot air, while in the tank system this chamber is heated by a tank of warmed water.

(a)Hot-Water Incubators.â€”In 1866 Colonel Stuart Wortley described inThe Fieldan incubator constructed upon a novel principle, but which appears never to have been adopted by breeders. The descriptive article is illustrated with a sketch. Essentially the incubator consists of four pipes which extend across the egg chamber some little distance above the eggs. The pipes pass through holes in the side of the incubator, which are furnished with pads, so as to render their passage air-tight. Externally they are connected with a boiler. This is provided with a dome through which steam escapes, and also with a glass gauge to show the height of the water within the boiler. The water in the boiler is kept at the boiling point, and the temperature of the incubator is regulated by adjustment of the length of the hot-water pipes within the egg chamber. To raise the temperature, a greater length of the pipes is pushed into the chamber, and to reduce it, more of their length is pulled outwards. It is claimed for this instrument that since the temperature of boiling water at any particular locality remains practically constant, the disadvantages due to fluctuations in the activity of a lamp flame or the size of a gas flame are obviated. But it has the serious disadvantage that there is no automatic adjustment to compensate for fluctuations of atmospheric temperature. And experiments by C. Hearson have shown that even if the temperature of the tank or source of heat be constant, that of the incubator drawer will nevertheless vary with fluctuations of external temperature. Probably if the mechanical difficulties of providing a self-regulator were overcome, it would prove an efficient and reliable incubator. The difficulties do not seem to be insuperable, and it appears possible that a thermostatic bar could be so arranged as to automatically increase or decrease the length of hot-water pipes within the incubator, and therefore the incubator temperature.Another early form of incubator is Brindleyâ€™s, which was first inuse about 1845, and in his hands it appeared occasionally to act successfully, but it never became generally used. The egg chamber was lined with felt, and was placed beneath a heated air chamber, the floor and roof of which were composed of glass. The air chamber was heated by a number of hot-water pipes which were connected with a copper boiler. This latter was heated by means of a lamp so constructed as to burn steadily. The temperature of the air chamber was regulated within certain limits by means of a balanced valve, which could be so adjusted that it would open at any desired temperature.In Colonel Stuart Wortleyâ€™s incubator the hot-water tubes passed directly into the egg chamber, and in Brindleyâ€™s into a chamber above it. But in other forms of incubators in which the principle of an external boiler connected with water tubes is adopted, the latter pass not into the egg chamber nor into an air chamber, but open into and from a tank of water. The floor of this tank forms the roof of the egg chamber, so that the eggs are heated from above. This device of warming the eggs from above was adopted in imitation of the processes that presumably occur with the sitting hen; for it is generally assumed that the surface of the eggs in contact with the hen is warmer than that in contact with the damp soil or with the material of the nest.One of the earliest of this form of incubator is that invented by F. SchrÃ¶der, manager of the now extinct British National Poultry Company. In this incubator the form is circular, and there are four egg drawers, so that each one occupied the quadrant of a circle, and the inner corner of each drawer meets in the middle of the incubator. From the centre of the incubator a vertical chimney passes upwards and opens out from the inner corners of the four egg drawers. This chimney acts as a ventilator to the incubating chambers. These latter are open above, but their floors are made of perforated zinc, and when in use they are partially filled with chaff or similar material. Under them is a tank containing cold water and common to all four drawers; the slight vapour rising from the surface of the water diffuses through the egg drawers and thus insures a sufficient degree of humidity to the air within. Above the egg drawers is a circular tank containing warm water. The floor of this tank constitutes the roof of the egg drawers, while the roof forms the floor of a circular chamber above it, the side wall of which is composed of perforated zinc. This upper chamber is used to dry the chicks when they are just hatched and to rear them until they are strong enough for removal. It is partially filled with sand, which serves the double purpose of retaining the heat in the warm-water tank beneath and of forming a bed for the chicks. The water in the warm-water tank is heated by means of a boiler which is external to the incubator, and in communication with the tank by means of an inlet and an outlet pipe. There is no valve to regulate the temperature, and the latter is measured by means of a thermometer, the bulb of which is situated not in the incubator drawers, but in the warm-water tank. This is a wrong position for the thermometer, since it is now known that the temperature of the water tank may be different by several degrees to that of the egg drawer; for with a fall of external temperature that of the latter necessarily tends to fall more rapidly than the former. But, none the less, in skilful hands this incubator gave good results.Fig. 1.â€”Christyâ€™s Improved Incubator.T. Christyâ€™s incubator, which we shall describe next, has passed through several forms. We shall consider the most recent one (1894). The incubator (fig. 1) is double walled, and the space between the two walls is packed with a non-conducting material. In the upper part of the incubator there is a water tank (T) divided by a horizontal partition into two chambers, communicating with each other at the left-hand side. Below the tank is the incubation drawer (E), which contains the eggs and also a temperature regulator or thermostat (R). The tank is traversed by a ventilating shaft (V), and inserted into this is a smaller sliding tube passing up to it from a hole in the bottom of the incubator drawer. The floor of the incubator drawer is perforated, and beneath it is an enclosed air space which opens into the sliding air shaft just described. Fresh air is let into the incubator drawer from a few apertures (I) at its top. The ventilating shaft (V) is closed externally by a cap (C), which can be raised from or lowered down upon its orifice by the horizontal arm (H) working upon pivot joints at (P). This arm is operated by the thermostat (R), through the agency of a vertical rod. The water in the tank is heated by an external boiler (B) through two pipes, one of which (T) serves as an inlet, and the other (L) as an outlet channel from the tank. These two pipes do not open directly into the tank, but into an outer vessel (O) communicating with it. Communication between this vessel and the tank may be made or broken by means of a sliding valve (S), which is pierced by an aperture that corresponds in position with the upper of the two in the wall of the tank when the valve is up. When this valve is in its upper position, the tank (T) communicates with the outer vessel (O) by two apertures (A and Aâ€²), the top one being the inlet and the lower one the outlet. These coincide in position with the tubes from the boiler. This latter (B) is a conical vessel containing two spaces. The heated water is contained in the outer of these spaces, while the central space is an air shaft heated by a lamp flame. This particular form of the boiler results in the water at its top part being more heated than that in its lower. As a consequence of this, a continual circulation of water through the tank ensues. The more heated water, being specifically lighter, passes into the outer vessel, where it remains among the higher strata, and therefore enters the tank through the upper aperture. In passing along the upper division of the tank it becomes slightly cooled and sinks therefore into the lower compartment, passes along it, and out through the aperture Aâ€². Hence it passes into the lower portion of the boiler, where it becomes warmed and specifically lighter; in consequence it becomes pushed upwards in the boiler by the cooler and heavier water coming in behind and below it.Should the temperature in the incubator drawer rise, the bimetallic thermostat (R) opens out its coil and pulls down the vertical rod. This simultaneously effects two things: it raises the cap (C) over the ventilating shaft and allows of a more rapid flow of fresh air through the incubator drawer, and it also lowers the slide-valve (S) so that the tank becomes cut off from communication with the outer vessel (O) and therefore with the boiler. The temperature thereupon begins to fall and the thermostat, coiling closer, raises the vertical rod, closes the ventilating shaft, and once more places the tank in communication with the boiler.The structure of the thermostat is given below.The Chantry Incubator (Sheffield) is also an incubator with a hot-water tank, the circulation of which is maintained by an outside boiler. Its temperature is regulated by a metal regulator.In SchrÃ¶derâ€™s and Christyâ€™s incubators the hot-water pipes from the boiler simply entered the warm-water tank but did not traverse it. In the two incubators to be next described the hot-water pipes are made to pass through the water in the tank, and are so arranged as to minimize the possibility that the outside of the tank may become colder than the centre. Both of them are also fitted with an ingenious though slightly complex valve for maintaining an approximately constant temperature.Halstedâ€™s incubator was the earliest of this type. Since his original form was constructed he has designed an improved one, and it is this latter which will be described.Fig 2.â€”Halstedâ€™s Incubator.The egg drawer (E, fig. 2) lies beneath the warm-water tank (T), and above this is a nursery (N). The egg drawer is ventilated by two tubular shafts (V), of which only one is represented in the illustration; the tubes are about 2Â½ in. in diameter, and each one is fitted at its upper end, where it opens into the nursery, with a swing-valve (Vâ€²) which turns upon a horizontal axis (A), in its turn connected, by means of cranks (C) and shafts (S), with the heat regulating apparatus (R). A space of about 2 in. between the top of the incubating drawer and the warm-water tank is necessary for the insertion of this apparatus. The water in the tank (T) is heated by means of the boiler (B); the tank and boiler are connected by the two pipes (I) and (O), of which one is the inlet and the other the outlet channel. The boiler consists of an inner (Iâ€²) and an outer (O) division in communication with each other below. The latter is cylindrical in form, while the outer wall of the former is cylindrical and its inner wall conical. The conical wall of the inner boiler is the surface which is heated by the lamp (L). The arrangement of the inlet and outlet tubes is important. In the illustration, for the sake of clearness, they are represented as one above the other. In reality they lie in the same plane, and the fork (F) of the inlet pipe similarly lies in the horizontal plane and not vertically as represented. The inlet pipe not only differs from the outlet pipe in thepossession of a forked end, but it is carried to the farther end (not shown in the diagram) of the water tank, while the outlet pipe opens from about the middle of the tank. The inlet pipe is connected with the inner portion of the boiler and the outlet one with the outer portion. The result of this adjustment of the parts is that the warmer water of the inner boiler, being specifically lighter than the cooler water of the outer boiler, rises up and passes through the inlet pipe (I) and is discharged into the tank through the two divergent orifices of the fork (F). Here the water strikes the side wall of the farther end of the tank and is reflected back along the back and front walls towards the nearer side. Hence it is again reflected, but in the opposite direction, and now forms a central current, which is directed towards the centrally situated orifice of the outlet tube (O). Through this it passes to the outer boiler, and sinking towards the bottom, reaches the base of the inner boiler. Here it becomes heated and lighter and consequently rises to the top, and once more passes through the inlet pipe to the water tank. The warm water thus travels round the outer walls of the tank and the cooled water is conducted away along the middle portion. A more equable distribution of temperature over the roof of the incubating chamber is thus ensured than would be the case if the heated water were discharged either into the centre or at any other single point only of the tank.To a very large extent, the efficiency of this apparatus depends upon the approximately perfect performance of the lamp. A good, steadily burning one should be employed, and only the best oil used; for, should the wick become fouled the flame cannot freely burn. For this reason it is better to use gas, whenever obtainable.The maintenance of an approximately uniform temperature is obtained by allowing the heated air of the egg-drawer to escape through the two ventilating shafts (V). The swing-valves of these are opened or closed by means of the regulator (R). This latter consists of a glass bowl prolonged into a tube, about 8 in. long and three-eighths of an inch in diameter. The glass tube swings upon an axis (A) which is situated as near as possible to the bowl of the regulator. The axis is connected with a crank (Câ€²) which is disposed so as to act as a lever upon the vertical shaft (S), which in its turn is connected with the upper crank (C); this works the axis (Aâ€²) of the swing-valves, and so can open or close the apertures of the ventilating pipes. The bowl of the regulator is filled with mercury to such an extent that at the temperature of 100Â° F., and when the tube is slightly inclined upwards from the horizontal it just flows slightly into the tube from the bowl. On the lever-crank (Câ€²) a weight is slung by a sliding adjustment, and is so placed that when the temperature of the egg-drawer is 103Â° it just balances the tube of the regulator when it is slightly inclined upwards. Should the temperature of the drawer now rise higher the mercury flows towards the distant end of the tube and, causing it to fall down, brings about a rotation of the regulator axis and as a consequence the opening of the ventilating valves. A transverse stay prevents the limb of the regulator from quite reaching the horizontal when it falls. As the temperature cools down the mercury contracts and retraces to the nearer end of the tube and to the bowl, and consequently results in the upward inclination of the limb; the valves are thus closed again.The egg-drawer (E) is specially constructed so as to imitate as nearly as possible the natural conditions that exist under a sitting hen. The drawer is of wood and contains a zinc tray (Z) into which cold water is placed. Fitting into the zinc tray is another zinc compartment, the floor of which is made of a number of zinc strips (X) transversely arranged and placed in relation to each other like the limbs of an inverted Î›. The limbs are so disposed that those of one series do not touch the adjacent ones, and in fact a space is left between them. Thus a number of parallel troughs are formed, each of which opens below into the moist air chamber of the cold water tray beneath. In practice these troughs are covered with flannel which is allowed to dip into the water of the tray. Thus the eggs lie in a series of damp troughs and their lower surfaces are therefore damper and colder than their upper ones. This incubator, if carefully worked and the necessary practical details observed, has the reputation of being an efficient machine.Somewhat similar to the Halsted incubator, but differing from it in the nature of the boiler and in the temperature regulator, is the Graves incubator, made in Boston, U.S.A. The incubator itself (fig. 3) consists of an incubating or egg-drawer (E) heated from above by a warm-water tank (T). Below the egg-drawer is a tank containing cold water, the vapour of which passes through the perforated floor of the former and keeps the air of the egg-chamber slightly humid. Above the warm-water tank is an air chamber (AC) to serve as a non-conducting medium and to prevent therefore undue loss of heat. Above this is a nursery or drying chamber (N), closed in, with a movable lid.The warm-water tank is heated by means of a simple boiler (B) from which an inlet tube (I) carries heated water to the tank; the tube traverses the length of the tank and discharges at its farther end (not shown in the diagram). From the nearer end of the tank an outlet tube (O) passes out and opens into the boiler at a slightly higher level than the inlet one. The boiler is heated by an evenly burning lamp below, of special construction. The rectangular tube through which the wick passes is bevelled at its outer end, and upon this bevelled edge a metal flap (F) is allowed to rest more or less closely, according as the flame is to be smaller or larger respectively. The wick is, of course, bevelled to correspond to the form of its tube. The metal flap is raised or depressed by means of levers connected with the heat-regulator. When it is depressed upon the wick the flame is lessened; and it becomes proportionately bigger as the flap is raised more and more.Fig. 3.â€”Gravesâ€™s Incubator.The heat-regulator consists of a glass tube (T) which runs the whole width of the incubation chamber and lies in contact with the floor of the warm-water tank; it is filled with alcohol. Externally to the incubator this tube is connected with aU-shaped one containing mercury. The free limb of theU-tube contains a piston (P) which rests upon the surface of the mercury in that limb. From the piston a piston rod (PR) passes vertically upwards and is connected with a lever (L) which operates, through the agency of a second lever (Lâ€²) the movements of the ventilating valve (V) inserted over the orifice of the ventilating shaft (A) which opens from the roof of the incubator drawer. The lever (L) is further connected with a spiral spring (S) which works the metal flap of the lamp already described. The height of the piston in theUtube can be so adjusted, by varying the quantity of mercury in the tube, that when the temperature of the incubation drawer is 103Â° F., the ventilating valves are closed and the wick is burning to its full extent. Should the temperature rise, the alcohol in the glass tube (T) expands and causes the mercury in the free limb of theUtube to rise. This carries with it the piston, and this movement brings about the opening of the ventilating valves, and at the same time, through the agency of the lever (L) and the spiral spring (S) the metal flap is brought down upon the wick, cutting off more or less of the flame. Should the temperature then fall to 103Â° or lower, the contraction of the alcohol reverses these movements, the valve closes, and the wick once more burns to its full extent.In practice, the boiler and the temperature regulator are duplicated, there being a set on both sides of the incubator. Any slight irregularity on the one side may be thus compensated for by the other side.Gravesâ€™s incubator has the reputation of being a good machine.Among the most recent type of incubators made in England is that of Charles Hearson. This differs from any of those described in the simplicity and ingenuity of the heat regulator, and in that the tubes which traverse the water tank are hot-air flues, carrying the air heated by the flame and not warm water. Consequently a further simplification is introduced inasmuch as no boiler is required.Fig. 4.â€”Hearsonâ€™s Incubator.The essential features of this incubator are shown in fig. 4. The internal parts of the incubator are insulated by a double wall, the interspace being packed by a non-conducting material, which is not shown in the figure. The incubation or egg-drawer (E) is heated by the warm-water tank (T). Beneath the egg-drawer is a zinc tray (Z), so constructed that in the central part the floor is raised up into a short cylinder. Around the raised cylinder is a wide trough containing water and into this dips a canvas cloth which is stretched out over a perforated zinc support (F). By this means an extended moistened surface is produced which allows of a rapid evaporation.The floor of the incubator, which is raised by short feet from the table on which it stands, is perforated in the central portion by a number of holes, and which are so situated that they lie beneath the raised cylinder of the cold-water tray (Z). The incubation-drawer is thus supplied continuously by a slow current of moistened air because the air in the upper part of the drawer,i.e.in contact with the floor of the warm-water tank, is the warmest and lightest. It therefore tends to diffuse or pass through the narrow slits between the drawer and the walls of the incubator, and also through the aperture in the front wall of the egg-drawer, through which a thermometer is laced. To replace the air thus lost, fresh air passes in through the holes in the bottom of the incubator, and on its way must pass through the pores of the damp canvas which dips into the water in the zinc tray (Z).The warm-water tank is heated by an inlet (I) and outlet (O) flue which are, however, continuous. The inlet flue opens out from a vertical chimney (C), the air in which is heated either by a gas flame or that of an oil lamp. The outlet or return flue passes back through the width of the tank and opens independently to the exterior. The vertical chimney (C) is capped by a lid (L) capable of being raised or lowered upon its orifice by the lever (Lâ€²). When the cap is resting upon the chimney all the heated air from within the latter passes through the flues and heats the water in the tank. If the cap is widely raised, practically all the heated air passes directly upwards through the chimney and none goes through the flues. If the cap be but slightly raised, part of the heated air goes through the flues and part directly escapes through the aperture of the chimney. The movement of the lever (Lâ€²) which raises the cap (L) is determined by the thermostatic capsule (S), situated within the egg-drawer.The principle upon which this capsule is designed is that the boiling point of a liquid depends not only upon temperature but also upon pressure. A given liquid at ordinary atmospheric pressure will boil at a certain degree of temperature, which varies for different substances. But if the pressure be increased the boiling point of the liquid is raised to a higher degree of temperature. A liquid when it boils passes into a gaseous condition and in this state will occupy a very much larger volumeâ€”some two or three hundred timesâ€”than in the liquid condition. If, therefore, a hermetically sealed capsule with flexible sides be filled with some liquid which boils at a given temperature, the sides of the capsule will distend when the temperature of the air round the capsule has been raised to the boiling point of the liquid within it. The distension of this capsule can be used to raise the lever (Lâ€²). The thermostatic capsule is placed on a fixed cradle (F) and is filled with a mixture of ether and alcohol, the proportions being such that the boiling point of the mixed liquid is 100Â° F. Between the capsule and the lever (Lâ€²) is a vertical rod (V), articulating with the lever as close as possible to its fulcrum (M). The articulation with the lever is by means of a screw, so that the necessary nice adjustment between the height of the rod (V), the thickness of the capsule and the position of rest of the damper (L) upon the chimney, can be accurately made. The temperature at which it is desired that the liquid in the capsule shall boil can be determined by sliding the weight (W) nearer or farther to the fulcrum of the lever (Lâ€²). The farther it is moved outwards, the greater is the pressure upon the thermostatic capsule and consequently the higher will be the boiling point of its contained liquid. By means of the milled-head screw (A), the height of the lever at its outer end can be so adjusted that when the liquid of the capsule is not boiling the damper (L) closes the chimney, but that when it does boil the damper will be raised sufficiently high from it. If the weight is pushed as far as it will go towards the fulcrum end of the lever, the temperature of the egg-drawer will never rise more than 100Â° F. because at this temperature and under the pressure to which it is then subjected, the liquid in the capsule boils, and consequently brings about the raising of the damper. It matters not, therefore, how high the flame of the gas or lamp be turned, the temperature of the egg-drawer will not increase, because the extra heat of the enlarged flame is passing directly outwards through the chimney, and is not going through the flues in the tank. In order to raise the temperature within the incubation chamber to 102Â° or 103Â°, or any other desired degree, the weight (W) must be moved outwards along the lever (Lâ€²), about 1 in. for every degree of temperature increase desired. This thermostatic capsule works admirably, and the incubator will work for months at a time and requires no adjustment, however much, within the limits of our climate, the external temperature may vary. The capsule, like all other thermostats in which the expansible substance is a liquid, is, however, dependent upon external pressure for the point at which its contained liquid boils and therefore, for the degree of temperature prevailing within the incubator drawer. It is therefore responsive to variations in atmospheric pressure, and as the barometer may fall 1 or 2 in., this may possibly make a difference of two or three degrees in the fluctuation of temperature within the egg-drawer. It is not, of course, often that such large oscillations of the barometer occur, and as a matter of practical experience, under ordinary conditions, this incubator will work for months together without attention with only half a degree variation round the point at which it was set.Fig. 5.â€”The Bedford (Greenwoodâ€™s) Incubator.Greenwoodâ€™s incubator (fig. 5), named the Bedford, resembles Pearsonâ€™s in that hot-air flues (F and Fâ€²) and not hot-water pipes, traverse the water tank (T). And the method of regulation of the temperature is much the same,i.e.a thermostat (V) operating upon a lever which raises a cap (C) from off the aperture of the main flue (F) and thus allows all the heat of the flame to pass directly outwards, without passing through the series of flues (F) which horizontally traverse the water-tank. Fresh air enters through a wide circular aperture (A) which surrounds the main flue, and it thus becomes partially warmed before entering the egg-chamber. The eggs are placed upon a perforated floor (E) lying over water baths (B). The water tank (T) lies in the centre of the incubation chamber and is traversed through its central axis by the main hot-air flue (F). From this, four horizontal flues pass outwards through the water and open into small vertical flues, which in their turn communicate with the exterior.The thermostat (V) consists of a glass tube of peculiar form. This is closed at the end of its short limb and open at its other extremity on the long limb. The bent portion of the tube is filled with mercury and between the mercury column and the closed end is a small quantity of ether. The thermostat is lodged in a box (G), which forms part of the lever (L). At one end this lever is pivoted to a fixed arm, and at the other to the vertical rod which operates the ventilating cap (C). If the temperature should rise, the ether in the thermostat expands and pushes the mercury column up along the inclined long limb. This disturbs the equilibrium of the lever (L), and it descends downwards, pulling with it the vertical rod, and thus raising the cap over the main flue. If the temperature falls the reverse series of changes occur. The temperature at which the cap will be raised can be adjusted within limits by the position of the weight (W) and by the adjustment of the degree of inclination of the thermostat.The Proctor incubator, made at Otley, is apparently, in its main features, similar to the Greenwood.Fig. 6.â€”The Winchcombe Incubator.Somewhat similar, in certain features, to the Greenwood is the Winchcombe. Its improved form, in which metal replaces the wood casing, is named the Gladstone. In it there is a combination of the hot-air and the water-tank systems of warming the incubation chamber. The wall of the incubator is double, and the space between the outer and inner wall is packed with a non-conducting material. The incubation chamber is heated above by a water-tank (fig. 6 T) which is traversed by a main vertical flue (F) and four subsidiary horizontal ones which discharge externally. The main flue, however, in passing up to enter the water tank traverses the egg-chamber, and therefore serves to warm it, as in the hot-air type of incubator, by the heat of the flue itself. Around the lower half of the flue is a water vessel consisting of two concentric containers (C), holding water. In the space between these concentric containers, fresh air passes in through the aperture (A), and before it reaches the egg-chamber it passes through coarse canvas which dips into the water in the containers, and is therefore kept permanently moist. The containers are filled from a water tank (S) outside the incubator. Air passes out from the egg-chamber through the aperture (O). The temperature is regulated by a bimetallic thermostat (see below), which operates two levers, that by their arrangement can raise or depress the cap (D) over the main flue (F). The temperature at which this occurs will be determined, within limits, by the position of the adjustable weight (W).Tomlinsonâ€™s incubator, designed in 1880, is novel in principle.It possesses a very large water tank, holding 15 gallons for every hundred eggs. Through this tank there pass two hot-air horizontal flues, lying in the same plane. The novelty of the construction lies in the great volume of water used and in the disposition of the flues towards the top of the tank. It is said that very little circulation of water takes place beneath the flues, because warmed water rises instead of falling. The great body of water below the flues will therefore only take up heat relatively slowly, and will, on account of its bulk and its physical properties, but slowly lose it. Should the flame fall in power, or even go out for ten or twelve hours, it is claimed that no serious loss of efficiency of the apparatus will result.Regulation of the temperature is by means of an air tube, the air in which expanding bulges out an india-rubber diaphragm and this moves a lever. The lever operates a valve which allows more or less of the heated air to escape from the egg-drawer.Fig. 7.â€”Hillierâ€™s Incubator.(b)Hot-air Incubators.â€”W. H. Hillierâ€™s Incubator (fig. 7) is circular in form and is constructed of a double-walled metal case. The space between the two walls is packed with a non-conducting material. The incubation or egg-chamber (C) is warmed by a circular heating box (H), and the air in this is heated by a lamp. The roof of this box forms part of the floor of the incubation chamber and from it a main flue (F) and four smaller ones (Fâ€²) pass upwards through the roof of the incubator and discharge to the exterior. Fresh air passes in to the incubator through two tubular channels (A and Aâ€²) on either side of the heating box and escapes through a hole in the roof, which serves at the same time as a passage for one of the rods (D) in connexion with the temperature regulating apparatus.This apparatus (T) consists of a glass tube of Â½ in. bore, and which is bent into the form of a circle of 5 in. diameter. The tube is fastened to a wooden disk, which rotates upon a pivot and in so doing operates a vertical rod (D), which in its turn works the cap (V) which covers the orifice of the main flue. The tube is partly filled with mercury and is closed at one end. At this end there is contained some spirit. As the temperature rises, this expands and pushes the mercury column farther along the tube. The equilibrium of the position of rest is thus disturbed, and the wooden disk consequently rotates, carrying with it the vertical arm, the downward movement of which raises the cap (V) of the flue. The temperature at which it is desired that this valve shall uncover the flue, can be adjusted within the necessary limits by sliding the weight (W) along the horizontal arm and by the amount of mercury present in the bent tube. The air of the incubation chamber is rendered sufficiently moist by the evaporation of water in the vessel (G).In the Cornell incubator (New York) more personal attention is required than in other forms, since the ventilation of the egg-chamber is not wholly automatic but is regulated according to the results of observation. The great difficulty in ventilation is the proper combination of fresh air and moisture. The Cornell Incubator Company has endeavoured to obviate this difficulty by carrying out a series of observations on the rate at which evaporation occurs in incubating eggs under natural conditions. The rate of evaporation is measured by the size of the air-space within the egg-shell at successive days. This they have ascertained, and with their incubators they furnish a book of instructions in which diagrams showing the size of the air space on the 1st, 5th, 10th, 14th and 18th days are given. Examination of the eggs should therefore be made every two or three days, and the result compared with the diagrams. The incubator is provided with an adjustable ventilator and this should be so arranged that evaporation is neither too great nor too little. The ventilator should never be wholly closed, and if when closed to its minimum evaporation is still too great, then water should be placed in the moisture pans. In all cases lukewarm water should be placed in these on the 18th day and the ventilating slide opened wide.It will thus be seen that in this machine there is an attempt to do away with the addition of water to the incubator drawer during the greater part of the period of incubation, and to rely upon the aqueous vapour naturally present in the atmosphere. This attempt is based upon the fact that water vapour is lighter than air, and will therefore rise to the top in any enclosed volume of air. If the direction of the ventilating current is downwards in the incubation chamber, and if it is slow enough, it is thought that the water vapour will be sifted out and tend to accumulate to a sufficient extent in the chamber. In the Cornell incubator consequently the ventilating current passes first upward through an external heater in order to warm it, whence it is then deflected downwards into the egg-chamber and diffuses through its perforated bottom. Then it passes along a space beneath the chamber into a space in the left-hand wall of the incubator and out to the exterior through an adjustable and graduated ventilating slide.These incubators are hot-air machines, and the hot-air chamber is situated above the egg-drawer and is traversed by several flues opening out from a main one. The temperature regulating apparatus appears to be similar to that of Hearsonâ€™s machine and operates by a thermostat, which through the agency of levers opens or closes a valve over the main flue.The Westmeria incubators (Leighton Buzzard) are of two patterns. One type is built on the hot-air principle and the other on the hot-water system. In both forms the heated air from the heating surfaces is deflected down on the eggs and escapes through the perforated bottom of the egg-drawer. The inlet air is first warmed by contact with the main flue. The thermostat is similar to that in the Hillier machine (fig. 7) and consists of a coil mounted on an axis, round which it can rotate. The coil is filled with mercury and is closed at one end. Between this end and the mercury column is a short column of air. By expansion of the air under a rising temperature, the mercury column is displaced and brings about a rotation of the disk to which the coiled tube containing it is attached. This rotation raises the cap over the main flue.All the incubators so far described have been constructed with the idea of obtaining as nearly as possible a uniform temperature. But in E. S. Renwickâ€™s incubator (America) no attempt is made to obtain uniformity in temperature. On the other hand, it is designed to give a periodical oscillation from one extreme to the other of a limited range, about 3Â°, of temperature. This is accomplished by means of a thermostatic bar made of plates of brass and vulcanite fastened together. This is connected with a clockwork and detent arrangement, which simultaneously opens a valve and actuates the lamp flame. The temperature falls to the lower limit of its range before the thermostatic bar is sufficiently bent to set the clockwork arrangement operating in the reverse direction, by which the valve is closed and the lamp flame increased. The temperature then rises to the higher limit, when the bending of the thermostatic bar again releases the detent and the clockwork opens the valve and reduces the flame.The incubator is said to succeed well. It also possesses a mechanical arrangement by which all the eggs can be periodically turned on rollers at once.Size.â€”The incubators which have been described are of relatively small size, and the numbers of eggs which they can incubate are strictly limited. For commercial purposes, however, operations of a much larger magnitude are desirable and necessary. And there can be no doubt that for these purposes the incubators of the future will be of great size and will contain from 15,000 to 30,000 eggs or more at a time. Already, at Aratoma Farm, Stamford, New York State, there is established a large incubation room, containing several thousands of eggs, and in which the heat regulation is controlled in part by the personal efforts of attendants. It constitutes almost a complete return, with added accessories, to the methods of the Egyptians, and to those of John Champion.

Another early form of incubator is Brindleyâ€™s, which was first inuse about 1845, and in his hands it appeared occasionally to act successfully, but it never became generally used. The egg chamber was lined with felt, and was placed beneath a heated air chamber, the floor and roof of which were composed of glass. The air chamber was heated by a number of hot-water pipes which were connected with a copper boiler. This latter was heated by means of a lamp so constructed as to burn steadily. The temperature of the air chamber was regulated within certain limits by means of a balanced valve, which could be so adjusted that it would open at any desired temperature.

In Colonel Stuart Wortleyâ€™s incubator the hot-water tubes passed directly into the egg chamber, and in Brindleyâ€™s into a chamber above it. But in other forms of incubators in which the principle of an external boiler connected with water tubes is adopted, the latter pass not into the egg chamber nor into an air chamber, but open into and from a tank of water. The floor of this tank forms the roof of the egg chamber, so that the eggs are heated from above. This device of warming the eggs from above was adopted in imitation of the processes that presumably occur with the sitting hen; for it is generally assumed that the surface of the eggs in contact with the hen is warmer than that in contact with the damp soil or with the material of the nest.

One of the earliest of this form of incubator is that invented by F. SchrÃ¶der, manager of the now extinct British National Poultry Company. In this incubator the form is circular, and there are four egg drawers, so that each one occupied the quadrant of a circle, and the inner corner of each drawer meets in the middle of the incubator. From the centre of the incubator a vertical chimney passes upwards and opens out from the inner corners of the four egg drawers. This chimney acts as a ventilator to the incubating chambers. These latter are open above, but their floors are made of perforated zinc, and when in use they are partially filled with chaff or similar material. Under them is a tank containing cold water and common to all four drawers; the slight vapour rising from the surface of the water diffuses through the egg drawers and thus insures a sufficient degree of humidity to the air within. Above the egg drawers is a circular tank containing warm water. The floor of this tank constitutes the roof of the egg drawers, while the roof forms the floor of a circular chamber above it, the side wall of which is composed of perforated zinc. This upper chamber is used to dry the chicks when they are just hatched and to rear them until they are strong enough for removal. It is partially filled with sand, which serves the double purpose of retaining the heat in the warm-water tank beneath and of forming a bed for the chicks. The water in the warm-water tank is heated by means of a boiler which is external to the incubator, and in communication with the tank by means of an inlet and an outlet pipe. There is no valve to regulate the temperature, and the latter is measured by means of a thermometer, the bulb of which is situated not in the incubator drawers, but in the warm-water tank. This is a wrong position for the thermometer, since it is now known that the temperature of the water tank may be different by several degrees to that of the egg drawer; for with a fall of external temperature that of the latter necessarily tends to fall more rapidly than the former. But, none the less, in skilful hands this incubator gave good results.

T. Christyâ€™s incubator, which we shall describe next, has passed through several forms. We shall consider the most recent one (1894). The incubator (fig. 1) is double walled, and the space between the two walls is packed with a non-conducting material. In the upper part of the incubator there is a water tank (T) divided by a horizontal partition into two chambers, communicating with each other at the left-hand side. Below the tank is the incubation drawer (E), which contains the eggs and also a temperature regulator or thermostat (R). The tank is traversed by a ventilating shaft (V), and inserted into this is a smaller sliding tube passing up to it from a hole in the bottom of the incubator drawer. The floor of the incubator drawer is perforated, and beneath it is an enclosed air space which opens into the sliding air shaft just described. Fresh air is let into the incubator drawer from a few apertures (I) at its top. The ventilating shaft (V) is closed externally by a cap (C), which can be raised from or lowered down upon its orifice by the horizontal arm (H) working upon pivot joints at (P). This arm is operated by the thermostat (R), through the agency of a vertical rod. The water in the tank is heated by an external boiler (B) through two pipes, one of which (T) serves as an inlet, and the other (L) as an outlet channel from the tank. These two pipes do not open directly into the tank, but into an outer vessel (O) communicating with it. Communication between this vessel and the tank may be made or broken by means of a sliding valve (S), which is pierced by an aperture that corresponds in position with the upper of the two in the wall of the tank when the valve is up. When this valve is in its upper position, the tank (T) communicates with the outer vessel (O) by two apertures (A and Aâ€²), the top one being the inlet and the lower one the outlet. These coincide in position with the tubes from the boiler. This latter (B) is a conical vessel containing two spaces. The heated water is contained in the outer of these spaces, while the central space is an air shaft heated by a lamp flame. This particular form of the boiler results in the water at its top part being more heated than that in its lower. As a consequence of this, a continual circulation of water through the tank ensues. The more heated water, being specifically lighter, passes into the outer vessel, where it remains among the higher strata, and therefore enters the tank through the upper aperture. In passing along the upper division of the tank it becomes slightly cooled and sinks therefore into the lower compartment, passes along it, and out through the aperture Aâ€². Hence it passes into the lower portion of the boiler, where it becomes warmed and specifically lighter; in consequence it becomes pushed upwards in the boiler by the cooler and heavier water coming in behind and below it.

Should the temperature in the incubator drawer rise, the bimetallic thermostat (R) opens out its coil and pulls down the vertical rod. This simultaneously effects two things: it raises the cap (C) over the ventilating shaft and allows of a more rapid flow of fresh air through the incubator drawer, and it also lowers the slide-valve (S) so that the tank becomes cut off from communication with the outer vessel (O) and therefore with the boiler. The temperature thereupon begins to fall and the thermostat, coiling closer, raises the vertical rod, closes the ventilating shaft, and once more places the tank in communication with the boiler.

The structure of the thermostat is given below.

The Chantry Incubator (Sheffield) is also an incubator with a hot-water tank, the circulation of which is maintained by an outside boiler. Its temperature is regulated by a metal regulator.

In SchrÃ¶derâ€™s and Christyâ€™s incubators the hot-water pipes from the boiler simply entered the warm-water tank but did not traverse it. In the two incubators to be next described the hot-water pipes are made to pass through the water in the tank, and are so arranged as to minimize the possibility that the outside of the tank may become colder than the centre. Both of them are also fitted with an ingenious though slightly complex valve for maintaining an approximately constant temperature.

Halstedâ€™s incubator was the earliest of this type. Since his original form was constructed he has designed an improved one, and it is this latter which will be described.

The egg drawer (E, fig. 2) lies beneath the warm-water tank (T), and above this is a nursery (N). The egg drawer is ventilated by two tubular shafts (V), of which only one is represented in the illustration; the tubes are about 2Â½ in. in diameter, and each one is fitted at its upper end, where it opens into the nursery, with a swing-valve (Vâ€²) which turns upon a horizontal axis (A), in its turn connected, by means of cranks (C) and shafts (S), with the heat regulating apparatus (R). A space of about 2 in. between the top of the incubating drawer and the warm-water tank is necessary for the insertion of this apparatus. The water in the tank (T) is heated by means of the boiler (B); the tank and boiler are connected by the two pipes (I) and (O), of which one is the inlet and the other the outlet channel. The boiler consists of an inner (Iâ€²) and an outer (O) division in communication with each other below. The latter is cylindrical in form, while the outer wall of the former is cylindrical and its inner wall conical. The conical wall of the inner boiler is the surface which is heated by the lamp (L). The arrangement of the inlet and outlet tubes is important. In the illustration, for the sake of clearness, they are represented as one above the other. In reality they lie in the same plane, and the fork (F) of the inlet pipe similarly lies in the horizontal plane and not vertically as represented. The inlet pipe not only differs from the outlet pipe in thepossession of a forked end, but it is carried to the farther end (not shown in the diagram) of the water tank, while the outlet pipe opens from about the middle of the tank. The inlet pipe is connected with the inner portion of the boiler and the outlet one with the outer portion. The result of this adjustment of the parts is that the warmer water of the inner boiler, being specifically lighter than the cooler water of the outer boiler, rises up and passes through the inlet pipe (I) and is discharged into the tank through the two divergent orifices of the fork (F). Here the water strikes the side wall of the farther end of the tank and is reflected back along the back and front walls towards the nearer side. Hence it is again reflected, but in the opposite direction, and now forms a central current, which is directed towards the centrally situated orifice of the outlet tube (O). Through this it passes to the outer boiler, and sinking towards the bottom, reaches the base of the inner boiler. Here it becomes heated and lighter and consequently rises to the top, and once more passes through the inlet pipe to the water tank. The warm water thus travels round the outer walls of the tank and the cooled water is conducted away along the middle portion. A more equable distribution of temperature over the roof of the incubating chamber is thus ensured than would be the case if the heated water were discharged either into the centre or at any other single point only of the tank.

To a very large extent, the efficiency of this apparatus depends upon the approximately perfect performance of the lamp. A good, steadily burning one should be employed, and only the best oil used; for, should the wick become fouled the flame cannot freely burn. For this reason it is better to use gas, whenever obtainable.

The maintenance of an approximately uniform temperature is obtained by allowing the heated air of the egg-drawer to escape through the two ventilating shafts (V). The swing-valves of these are opened or closed by means of the regulator (R). This latter consists of a glass bowl prolonged into a tube, about 8 in. long and three-eighths of an inch in diameter. The glass tube swings upon an axis (A) which is situated as near as possible to the bowl of the regulator. The axis is connected with a crank (Câ€²) which is disposed so as to act as a lever upon the vertical shaft (S), which in its turn is connected with the upper crank (C); this works the axis (Aâ€²) of the swing-valves, and so can open or close the apertures of the ventilating pipes. The bowl of the regulator is filled with mercury to such an extent that at the temperature of 100Â° F., and when the tube is slightly inclined upwards from the horizontal it just flows slightly into the tube from the bowl. On the lever-crank (Câ€²) a weight is slung by a sliding adjustment, and is so placed that when the temperature of the egg-drawer is 103Â° it just balances the tube of the regulator when it is slightly inclined upwards. Should the temperature of the drawer now rise higher the mercury flows towards the distant end of the tube and, causing it to fall down, brings about a rotation of the regulator axis and as a consequence the opening of the ventilating valves. A transverse stay prevents the limb of the regulator from quite reaching the horizontal when it falls. As the temperature cools down the mercury contracts and retraces to the nearer end of the tube and to the bowl, and consequently results in the upward inclination of the limb; the valves are thus closed again.

The egg-drawer (E) is specially constructed so as to imitate as nearly as possible the natural conditions that exist under a sitting hen. The drawer is of wood and contains a zinc tray (Z) into which cold water is placed. Fitting into the zinc tray is another zinc compartment, the floor of which is made of a number of zinc strips (X) transversely arranged and placed in relation to each other like the limbs of an inverted Î›. The limbs are so disposed that those of one series do not touch the adjacent ones, and in fact a space is left between them. Thus a number of parallel troughs are formed, each of which opens below into the moist air chamber of the cold water tray beneath. In practice these troughs are covered with flannel which is allowed to dip into the water of the tray. Thus the eggs lie in a series of damp troughs and their lower surfaces are therefore damper and colder than their upper ones. This incubator, if carefully worked and the necessary practical details observed, has the reputation of being an efficient machine.

Somewhat similar to the Halsted incubator, but differing from it in the nature of the boiler and in the temperature regulator, is the Graves incubator, made in Boston, U.S.A. The incubator itself (fig. 3) consists of an incubating or egg-drawer (E) heated from above by a warm-water tank (T). Below the egg-drawer is a tank containing cold water, the vapour of which passes through the perforated floor of the former and keeps the air of the egg-chamber slightly humid. Above the warm-water tank is an air chamber (AC) to serve as a non-conducting medium and to prevent therefore undue loss of heat. Above this is a nursery or drying chamber (N), closed in, with a movable lid.

The warm-water tank is heated by means of a simple boiler (B) from which an inlet tube (I) carries heated water to the tank; the tube traverses the length of the tank and discharges at its farther end (not shown in the diagram). From the nearer end of the tank an outlet tube (O) passes out and opens into the boiler at a slightly higher level than the inlet one. The boiler is heated by an evenly burning lamp below, of special construction. The rectangular tube through which the wick passes is bevelled at its outer end, and upon this bevelled edge a metal flap (F) is allowed to rest more or less closely, according as the flame is to be smaller or larger respectively. The wick is, of course, bevelled to correspond to the form of its tube. The metal flap is raised or depressed by means of levers connected with the heat-regulator. When it is depressed upon the wick the flame is lessened; and it becomes proportionately bigger as the flap is raised more and more.

The heat-regulator consists of a glass tube (T) which runs the whole width of the incubation chamber and lies in contact with the floor of the warm-water tank; it is filled with alcohol. Externally to the incubator this tube is connected with aU-shaped one containing mercury. The free limb of theU-tube contains a piston (P) which rests upon the surface of the mercury in that limb. From the piston a piston rod (PR) passes vertically upwards and is connected with a lever (L) which operates, through the agency of a second lever (Lâ€²) the movements of the ventilating valve (V) inserted over the orifice of the ventilating shaft (A) which opens from the roof of the incubator drawer. The lever (L) is further connected with a spiral spring (S) which works the metal flap of the lamp already described. The height of the piston in theUtube can be so adjusted, by varying the quantity of mercury in the tube, that when the temperature of the incubation drawer is 103Â° F., the ventilating valves are closed and the wick is burning to its full extent. Should the temperature rise, the alcohol in the glass tube (T) expands and causes the mercury in the free limb of theUtube to rise. This carries with it the piston, and this movement brings about the opening of the ventilating valves, and at the same time, through the agency of the lever (L) and the spiral spring (S) the metal flap is brought down upon the wick, cutting off more or less of the flame. Should the temperature then fall to 103Â° or lower, the contraction of the alcohol reverses these movements, the valve closes, and the wick once more burns to its full extent.

In practice, the boiler and the temperature regulator are duplicated, there being a set on both sides of the incubator. Any slight irregularity on the one side may be thus compensated for by the other side.

Gravesâ€™s incubator has the reputation of being a good machine.

Among the most recent type of incubators made in England is that of Charles Hearson. This differs from any of those described in the simplicity and ingenuity of the heat regulator, and in that the tubes which traverse the water tank are hot-air flues, carrying the air heated by the flame and not warm water. Consequently a further simplification is introduced inasmuch as no boiler is required.

The essential features of this incubator are shown in fig. 4. The internal parts of the incubator are insulated by a double wall, the interspace being packed by a non-conducting material, which is not shown in the figure. The incubation or egg-drawer (E) is heated by the warm-water tank (T). Beneath the egg-drawer is a zinc tray (Z), so constructed that in the central part the floor is raised up into a short cylinder. Around the raised cylinder is a wide trough containing water and into this dips a canvas cloth which is stretched out over a perforated zinc support (F). By this means an extended moistened surface is produced which allows of a rapid evaporation.The floor of the incubator, which is raised by short feet from the table on which it stands, is perforated in the central portion by a number of holes, and which are so situated that they lie beneath the raised cylinder of the cold-water tray (Z). The incubation-drawer is thus supplied continuously by a slow current of moistened air because the air in the upper part of the drawer,i.e.in contact with the floor of the warm-water tank, is the warmest and lightest. It therefore tends to diffuse or pass through the narrow slits between the drawer and the walls of the incubator, and also through the aperture in the front wall of the egg-drawer, through which a thermometer is laced. To replace the air thus lost, fresh air passes in through the holes in the bottom of the incubator, and on its way must pass through the pores of the damp canvas which dips into the water in the zinc tray (Z).

The warm-water tank is heated by an inlet (I) and outlet (O) flue which are, however, continuous. The inlet flue opens out from a vertical chimney (C), the air in which is heated either by a gas flame or that of an oil lamp. The outlet or return flue passes back through the width of the tank and opens independently to the exterior. The vertical chimney (C) is capped by a lid (L) capable of being raised or lowered upon its orifice by the lever (Lâ€²). When the cap is resting upon the chimney all the heated air from within the latter passes through the flues and heats the water in the tank. If the cap is widely raised, practically all the heated air passes directly upwards through the chimney and none goes through the flues. If the cap be but slightly raised, part of the heated air goes through the flues and part directly escapes through the aperture of the chimney. The movement of the lever (Lâ€²) which raises the cap (L) is determined by the thermostatic capsule (S), situated within the egg-drawer.

The principle upon which this capsule is designed is that the boiling point of a liquid depends not only upon temperature but also upon pressure. A given liquid at ordinary atmospheric pressure will boil at a certain degree of temperature, which varies for different substances. But if the pressure be increased the boiling point of the liquid is raised to a higher degree of temperature. A liquid when it boils passes into a gaseous condition and in this state will occupy a very much larger volumeâ€”some two or three hundred timesâ€”than in the liquid condition. If, therefore, a hermetically sealed capsule with flexible sides be filled with some liquid which boils at a given temperature, the sides of the capsule will distend when the temperature of the air round the capsule has been raised to the boiling point of the liquid within it. The distension of this capsule can be used to raise the lever (Lâ€²). The thermostatic capsule is placed on a fixed cradle (F) and is filled with a mixture of ether and alcohol, the proportions being such that the boiling point of the mixed liquid is 100Â° F. Between the capsule and the lever (Lâ€²) is a vertical rod (V), articulating with the lever as close as possible to its fulcrum (M). The articulation with the lever is by means of a screw, so that the necessary nice adjustment between the height of the rod (V), the thickness of the capsule and the position of rest of the damper (L) upon the chimney, can be accurately made. The temperature at which it is desired that the liquid in the capsule shall boil can be determined by sliding the weight (W) nearer or farther to the fulcrum of the lever (Lâ€²). The farther it is moved outwards, the greater is the pressure upon the thermostatic capsule and consequently the higher will be the boiling point of its contained liquid. By means of the milled-head screw (A), the height of the lever at its outer end can be so adjusted that when the liquid of the capsule is not boiling the damper (L) closes the chimney, but that when it does boil the damper will be raised sufficiently high from it. If the weight is pushed as far as it will go towards the fulcrum end of the lever, the temperature of the egg-drawer will never rise more than 100Â° F. because at this temperature and under the pressure to which it is then subjected, the liquid in the capsule boils, and consequently brings about the raising of the damper. It matters not, therefore, how high the flame of the gas or lamp be turned, the temperature of the egg-drawer will not increase, because the extra heat of the enlarged flame is passing directly outwards through the chimney, and is not going through the flues in the tank. In order to raise the temperature within the incubation chamber to 102Â° or 103Â°, or any other desired degree, the weight (W) must be moved outwards along the lever (Lâ€²), about 1 in. for every degree of temperature increase desired. This thermostatic capsule works admirably, and the incubator will work for months at a time and requires no adjustment, however much, within the limits of our climate, the external temperature may vary. The capsule, like all other thermostats in which the expansible substance is a liquid, is, however, dependent upon external pressure for the point at which its contained liquid boils and therefore, for the degree of temperature prevailing within the incubator drawer. It is therefore responsive to variations in atmospheric pressure, and as the barometer may fall 1 or 2 in., this may possibly make a difference of two or three degrees in the fluctuation of temperature within the egg-drawer. It is not, of course, often that such large oscillations of the barometer occur, and as a matter of practical experience, under ordinary conditions, this incubator will work for months together without attention with only half a degree variation round the point at which it was set.

Greenwoodâ€™s incubator (fig. 5), named the Bedford, resembles Pearsonâ€™s in that hot-air flues (F and Fâ€²) and not hot-water pipes, traverse the water tank (T). And the method of regulation of the temperature is much the same,i.e.a thermostat (V) operating upon a lever which raises a cap (C) from off the aperture of the main flue (F) and thus allows all the heat of the flame to pass directly outwards, without passing through the series of flues (F) which horizontally traverse the water-tank. Fresh air enters through a wide circular aperture (A) which surrounds the main flue, and it thus becomes partially warmed before entering the egg-chamber. The eggs are placed upon a perforated floor (E) lying over water baths (B). The water tank (T) lies in the centre of the incubation chamber and is traversed through its central axis by the main hot-air flue (F). From this, four horizontal flues pass outwards through the water and open into small vertical flues, which in their turn communicate with the exterior.

The thermostat (V) consists of a glass tube of peculiar form. This is closed at the end of its short limb and open at its other extremity on the long limb. The bent portion of the tube is filled with mercury and between the mercury column and the closed end is a small quantity of ether. The thermostat is lodged in a box (G), which forms part of the lever (L). At one end this lever is pivoted to a fixed arm, and at the other to the vertical rod which operates the ventilating cap (C). If the temperature should rise, the ether in the thermostat expands and pushes the mercury column up along the inclined long limb. This disturbs the equilibrium of the lever (L), and it descends downwards, pulling with it the vertical rod, and thus raising the cap over the main flue. If the temperature falls the reverse series of changes occur. The temperature at which the cap will be raised can be adjusted within limits by the position of the weight (W) and by the adjustment of the degree of inclination of the thermostat.

The Proctor incubator, made at Otley, is apparently, in its main features, similar to the Greenwood.

Somewhat similar, in certain features, to the Greenwood is the Winchcombe. Its improved form, in which metal replaces the wood casing, is named the Gladstone. In it there is a combination of the hot-air and the water-tank systems of warming the incubation chamber. The wall of the incubator is double, and the space between the outer and inner wall is packed with a non-conducting material. The incubation chamber is heated above by a water-tank (fig. 6 T) which is traversed by a main vertical flue (F) and four subsidiary horizontal ones which discharge externally. The main flue, however, in passing up to enter the water tank traverses the egg-chamber, and therefore serves to warm it, as in the hot-air type of incubator, by the heat of the flue itself. Around the lower half of the flue is a water vessel consisting of two concentric containers (C), holding water. In the space between these concentric containers, fresh air passes in through the aperture (A), and before it reaches the egg-chamber it passes through coarse canvas which dips into the water in the containers, and is therefore kept permanently moist. The containers are filled from a water tank (S) outside the incubator. Air passes out from the egg-chamber through the aperture (O). The temperature is regulated by a bimetallic thermostat (see below), which operates two levers, that by their arrangement can raise or depress the cap (D) over the main flue (F). The temperature at which this occurs will be determined, within limits, by the position of the adjustable weight (W).

Tomlinsonâ€™s incubator, designed in 1880, is novel in principle.It possesses a very large water tank, holding 15 gallons for every hundred eggs. Through this tank there pass two hot-air horizontal flues, lying in the same plane. The novelty of the construction lies in the great volume of water used and in the disposition of the flues towards the top of the tank. It is said that very little circulation of water takes place beneath the flues, because warmed water rises instead of falling. The great body of water below the flues will therefore only take up heat relatively slowly, and will, on account of its bulk and its physical properties, but slowly lose it. Should the flame fall in power, or even go out for ten or twelve hours, it is claimed that no serious loss of efficiency of the apparatus will result.

Regulation of the temperature is by means of an air tube, the air in which expanding bulges out an india-rubber diaphragm and this moves a lever. The lever operates a valve which allows more or less of the heated air to escape from the egg-drawer.

(b)Hot-air Incubators.â€”W. H. Hillierâ€™s Incubator (fig. 7) is circular in form and is constructed of a double-walled metal case. The space between the two walls is packed with a non-conducting material. The incubation or egg-chamber (C) is warmed by a circular heating box (H), and the air in this is heated by a lamp. The roof of this box forms part of the floor of the incubation chamber and from it a main flue (F) and four smaller ones (Fâ€²) pass upwards through the roof of the incubator and discharge to the exterior. Fresh air passes in to the incubator through two tubular channels (A and Aâ€²) on either side of the heating box and escapes through a hole in the roof, which serves at the same time as a passage for one of the rods (D) in connexion with the temperature regulating apparatus.

This apparatus (T) consists of a glass tube of Â½ in. bore, and which is bent into the form of a circle of 5 in. diameter. The tube is fastened to a wooden disk, which rotates upon a pivot and in so doing operates a vertical rod (D), which in its turn works the cap (V) which covers the orifice of the main flue. The tube is partly filled with mercury and is closed at one end. At this end there is contained some spirit. As the temperature rises, this expands and pushes the mercury column farther along the tube. The equilibrium of the position of rest is thus disturbed, and the wooden disk consequently rotates, carrying with it the vertical arm, the downward movement of which raises the cap (V) of the flue. The temperature at which it is desired that this valve shall uncover the flue, can be adjusted within the necessary limits by sliding the weight (W) along the horizontal arm and by the amount of mercury present in the bent tube. The air of the incubation chamber is rendered sufficiently moist by the evaporation of water in the vessel (G).

In the Cornell incubator (New York) more personal attention is required than in other forms, since the ventilation of the egg-chamber is not wholly automatic but is regulated according to the results of observation. The great difficulty in ventilation is the proper combination of fresh air and moisture. The Cornell Incubator Company has endeavoured to obviate this difficulty by carrying out a series of observations on the rate at which evaporation occurs in incubating eggs under natural conditions. The rate of evaporation is measured by the size of the air-space within the egg-shell at successive days. This they have ascertained, and with their incubators they furnish a book of instructions in which diagrams showing the size of the air space on the 1st, 5th, 10th, 14th and 18th days are given. Examination of the eggs should therefore be made every two or three days, and the result compared with the diagrams. The incubator is provided with an adjustable ventilator and this should be so arranged that evaporation is neither too great nor too little. The ventilator should never be wholly closed, and if when closed to its minimum evaporation is still too great, then water should be placed in the moisture pans. In all cases lukewarm water should be placed in these on the 18th day and the ventilating slide opened wide.

It will thus be seen that in this machine there is an attempt to do away with the addition of water to the incubator drawer during the greater part of the period of incubation, and to rely upon the aqueous vapour naturally present in the atmosphere. This attempt is based upon the fact that water vapour is lighter than air, and will therefore rise to the top in any enclosed volume of air. If the direction of the ventilating current is downwards in the incubation chamber, and if it is slow enough, it is thought that the water vapour will be sifted out and tend to accumulate to a sufficient extent in the chamber. In the Cornell incubator consequently the ventilating current passes first upward through an external heater in order to warm it, whence it is then deflected downwards into the egg-chamber and diffuses through its perforated bottom. Then it passes along a space beneath the chamber into a space in the left-hand wall of the incubator and out to the exterior through an adjustable and graduated ventilating slide.

These incubators are hot-air machines, and the hot-air chamber is situated above the egg-drawer and is traversed by several flues opening out from a main one. The temperature regulating apparatus appears to be similar to that of Hearsonâ€™s machine and operates by a thermostat, which through the agency of levers opens or closes a valve over the main flue.

The Westmeria incubators (Leighton Buzzard) are of two patterns. One type is built on the hot-air principle and the other on the hot-water system. In both forms the heated air from the heating surfaces is deflected down on the eggs and escapes through the perforated bottom of the egg-drawer. The inlet air is first warmed by contact with the main flue. The thermostat is similar to that in the Hillier machine (fig. 7) and consists of a coil mounted on an axis, round which it can rotate. The coil is filled with mercury and is closed at one end. Between this end and the mercury column is a short column of air. By expansion of the air under a rising temperature, the mercury column is displaced and brings about a rotation of the disk to which the coiled tube containing it is attached. This rotation raises the cap over the main flue.

All the incubators so far described have been constructed with the idea of obtaining as nearly as possible a uniform temperature. But in E. S. Renwickâ€™s incubator (America) no attempt is made to obtain uniformity in temperature. On the other hand, it is designed to give a periodical oscillation from one extreme to the other of a limited range, about 3Â°, of temperature. This is accomplished by means of a thermostatic bar made of plates of brass and vulcanite fastened together. This is connected with a clockwork and detent arrangement, which simultaneously opens a valve and actuates the lamp flame. The temperature falls to the lower limit of its range before the thermostatic bar is sufficiently bent to set the clockwork arrangement operating in the reverse direction, by which the valve is closed and the lamp flame increased. The temperature then rises to the higher limit, when the bending of the thermostatic bar again releases the detent and the clockwork opens the valve and reduces the flame.

The incubator is said to succeed well. It also possesses a mechanical arrangement by which all the eggs can be periodically turned on rollers at once.

Size.â€”The incubators which have been described are of relatively small size, and the numbers of eggs which they can incubate are strictly limited. For commercial purposes, however, operations of a much larger magnitude are desirable and necessary. And there can be no doubt that for these purposes the incubators of the future will be of great size and will contain from 15,000 to 30,000 eggs or more at a time. Already, at Aratoma Farm, Stamford, New York State, there is established a large incubation room, containing several thousands of eggs, and in which the heat regulation is controlled in part by the personal efforts of attendants. It constitutes almost a complete return, with added accessories, to the methods of the Egyptians, and to those of John Champion.

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