750 pounds of sugar.1,000 pounds of molasses.900 pounds of seed.1,500 pounds of fodder (green leaves).1,500 pounds of exhausted chips (dried). A total of 5,650 pounds.
750 pounds of sugar.1,000 pounds of molasses.900 pounds of seed.1,500 pounds of fodder (green leaves).1,500 pounds of exhausted chips (dried). A total of 5,650 pounds.
The first three items, which are as likely to be transported as wheat or corn, aggregate 2,650 pounds per acre.
Sorghum will yield seven and a half tons of cleaned cane per acre more surely than corn will yield thirty bushels or wheat fifteen bushels per acre.
In the comparison, then, of products which bear transportation, these crops stand as follows:
Sorghum, at 7½ tons, 2,650 pounds per acre.Corn, at 30 bushels, 1,680 pounds per acre.Wheat, at 15 bushels, 900 pounds per acre.
Sorghum, at 7½ tons, 2,650 pounds per acre.Corn, at 30 bushels, 1,680 pounds per acre.Wheat, at 15 bushels, 900 pounds per acre.
The sugar from the sorghum is worth say 5 cents per pound; the molasses, 1¾ cents per pound; the seed, ½ cent per pound.
The sorghum products give market values as follows:
750 pounds sugar at say 5 cents,2$37.50.1,000 pounds molasses at say 1¾ cents,2$17.50.900 pounds seed at say ½ cent,2$4.50.Total value of sorghum, less fodder, $59.50.The corn crop gives 1,680 pounds, at ½ cent $8.40.The wheat crop gives 900 pounds, at 1 cent, $9.
750 pounds sugar at say 5 cents,2$37.50.1,000 pounds molasses at say 1¾ cents,2$17.50.900 pounds seed at say ½ cent,2$4.50.Total value of sorghum, less fodder, $59.50.The corn crop gives 1,680 pounds, at ½ cent $8.40.The wheat crop gives 900 pounds, at 1 cent, $9.
Thus it will be seen that the sorghum yields to the farmer more than twice as much per acre as either of the leading cereals, and as a gross product of agriculture and manufacture on our own soil more than six times as much per acre as is usually realized from either of these standard crops.
[1]
For this improvement Prof. Swenson obtained a patent Oct. 11, 1887, the grant of which was recently made the subject of congressional inquiry.
For this improvement Prof. Swenson obtained a patent Oct. 11, 1887, the grant of which was recently made the subject of congressional inquiry.
[2]
The sugar sold this year at 5¾ cents per pound, the molasses at 20 cents per gallon, and the seed at —— per bushel of 56 pounds. The seed is of about equal value with corn for feeding stock.
The sugar sold this year at 5¾ cents per pound, the molasses at 20 cents per gallon, and the seed at —— per bushel of 56 pounds. The seed is of about equal value with corn for feeding stock.
A new process for producing iron and steel direct from the ore has been brought out in Russia. Under the new process iron ore, after being submitted to the smelting processes, is taken direct from the furnace to the rolling mill and turned into thin sheets of the finest charcoal iron. At present the process has only been commercially applied with charcoal fuel, but experiments are stated to have shown that equal success can be obtained with coke. The secret of the process lies in the construction of the furnace, which is said to be simple and inexpensive.
We have received from M. Menges (of the Hague) a most interesting description of an apparatus on which he has been at work for some time past, with the object of generating electricity by the direct conversion of heat, or, as it might be more accurately described, by a more direct conversion than that of an ordinary dynamo. M. Menges' apparatus depends, like that of Edison, upon the fact that the magnetic metals lose their magnetic permeability at a certain temperature.
It differs greatly, however, from its predecessor in important points, especially in the fact that it does not require the aid of any external source of motive power.
In Edison's pyromagnetic dynamo it will be remembered that it is necessary to provide some small amount of motive power from an extraneous source in order to revolve the shield by which the heat is alternately directed on one half or the other of the armature cores. M. Menges' apparatus is, on the contrary, wholly automatic.
We proceed to give a free translation of the description furnished us by the inventor.
In attempting to employ the thermo-magnetic properties of iron or nickel in the construction of machines for the generation of electricity upon an industrial scale, we are met with the difficulty that the heating and cooling of large masses of metal not only involves great loss of heat, but also requires much time. Hence, to obtain a useful effect of any importance, it would appear necessary to employ machines of dimensions altogether impracticable. By the device and method of construction now to be explained this difficulty has, however, been completely overcome.
The action of a magnetic pole diminishes so rapidly with the increase of distance that it may suffice to remove the armature to a distance relatively small compared with its own dimensions, or with those of the magnet, in order to reduce the action to a negligible value. But if the magnet, N S, and the armature, A, being at a certain distance, we bring between them a piece of iron or nickel,d, then the magnetic force upon A is immediately and very considerably increased. In modern language, the resistance of the magnetic circuit has been reduced by the introduction of a better magnetic conductor, and the number of lines of force passing through A is proportionately increased. The mass of the piece,d, may, moreover, be relatively small compared with that of N S and A. If d be again withdrawn, the magnetic resistance is increased, and the lines through A are again a minimum.
Now, it is evident that we can also obtain the same effect by sufficiently heating and cooling the intermediate piece,d; and again, with a broad field we can alter the distribution of the lines at will by heating or cooling one side of this piece or the other. For this reason we will call the piece d thethermo-magnetic distributor, or, briefly, the distributor.
We will now describe the manner in which this principle has been realized in the practical construction of both a thermo-magnetic generator and motor.
Fig. 1.Fig.1.
Fig. 1 shows an elevation and part section of one of the arrangements employed. Fig. 2 is a plan of the same machine (in the latter the ring,a a, appearing on a higher plane than it actually occupies).
Fig. 2.Fig.2.
N S is an electro-magnet,a athe armature, wound as a Gramme ring, and fixed to a frame with four arms, which can turn freely upon a pivot midway between the poles. The cross arms of the frame are attached at 1, 2, 3, 4, Fig. 2. Between the magnets and the armature is placed the distributor,d d, where it occupies an annular space open above and below. Both the magnets and the armature are coated on the sides facing the distributor with mica or some other non-conductor of heat and electricity. The distributor is attached to and supported by the cross arms, so that it turns with the armature.
The distributor is composed of a ribbon of iron or nickel, bent into a continuous zigzag. This form has the advantage of presenting, in the cool part of the distributor, an almost direct road for the lines of force between the poles and the armature, thus diminishing the magnetic resistance as far as possible. At the same time the Foucault currents are minimized. To the same end it is useful to slit the ribbon, as in Fig. 3. This also facilitates the folding into zigzags.
Fig. 3.Fig.3.
The distributor is heated at two opposite points on a diameter by the burners,b b, above which are the chimneys,e e. The cooling of the alternate section is aided by the circulation of cold air, which is effected by means of the draught in the chimneys,e e. At the points of lowest temperature a jet of air or water is maintained. The cross arms are insulated with mica or asbestos at the points where they extend from the armature to the distributor.
It will now be evident that while the distributor is entirely cool, many of the lines of force pass from N to S without entering the armature core; but if heat is applied at the points 1 and 2 in the figure, so as to increase the magnetic resistance at these points, then a great portion of the lines will leave the distributor, and pass through the armature core. Under these conditions, so long as heat is applied at two points equidistant from N and S, we might, if we so pleased, cause the armature to be rotated by an external source of power, and we should then have an E.M.F. generated in the armature coils—that is to say, the machine would work as an ordinary dynamo, and the power expended in driving the armature would be proportionate to the output.
Fig. 4.Fig.4.
Suppose next that the points of heating, and with them the alternate points of cooling 90 deg. apart, are shifted round about 45 deg., so that the two hot regions are no longer symmetrically situated in respect to each pole of the field. The distribution of the magnetization has therefore become unsymmetrical, and the iron core is no longer in equilibrium in the magnetic field. We have, in fact, the conditions of Schwedoff's experiment upon a larger scale, and if the forces are sufficient to overcome the frictional resistance, a rotation of the ring ensues in the endeavor to restore equilibrium. The regions of heating and cooling being fixed in space, this rotation is continuous so long as the difference of temperature is maintained. The ring in rotating carries with it the armature coils, and of course an E.M.F. is generated in the same way as if the motive power came from an external source. In this respect the machine therefore resembles a motor generator, and the rotation is entirely automatic.
The armature coils are connected with a commutator in the usual way, and the field may, of course, be excited either in shunt or in series. M. Menges says that the residual magnetization is sufficient in his machine to start the rotation by itself.
When the machine is to be used as a motor, it is evident that the windings on the armature core need only be sufficient to supply current to excite the field, or bythe use of permanent magnets they may be dispensed with altogether.
M. Menges has further designed a large number of variations on the original type, varying the arrangement of the several parts, and employing armatures and fields of many different types, such as are already in use for dynamos.
In Fig. 4 a machine is represented in which the field is external to the armature.
In Fig. 5 we have a thermo-magnetic generator, which corresponds to the disk machine in dynamos. Similar parts are indicated by the same letters in each of these figures, so that no further detailed description is necessary.
Fig. 5.Fig.5.
In another modification M. Menges proposes to rotate the burners and leave the armature and distributor at rest. But in this case it is evident that the E.M.F. produced would be much less, because the magnetization of the core would only undergo a variation of intensity, and would nowhere be reversed, except, perhaps, just in front of the poles. In machines modeled on the Brush type it is evident that the distributor need not be continuous.
Enough has, however, been said to indicate the extent of the field upon which the principle may be applied.—The Electrician.
I will try to give a short report of some experiments I have made during the last year in regard to atmospheric electricity. It was formerly uncertain whether the electrostatic potential would increase by rising from the surface of the earth to more elevated region of the atmosphere or not, and also whether the potential in a normal—that is, cloudless—state of the atmosphere was always positive or sometimes negative. Sir William Thomson found by exact methods of measuring that the increase of the potential with elevation is very important, and values about 100 volts per meter. That fact is proved by many other observers, especially lately by Mr. F. Exner, at Vienna, who found an increase of 60 to 600 volts per meter. The observations were made by means of an electrometer. In respect of many inconveniences which are connected with the use of an electrometer, I have tried the measurements with a very sensitive galvanometer. In this case it is necessary to apply a separating air exhaust apparatus, for example flame, or a system of points at the upper end of the conductor, which is elevated in the atmosphere. In order to get a constant apparatus, I have used 400 of the finest needles inserted in a metallic ribbon. This system I have raised in the air by means of a captive balloon, or by a kite, which was attached to a conductor of twine or to a twisted line of the finest steel wire. In this way I have attained a height of 100 to 300 meters. When the lower end of the kite line was communicating with the galvanometer whose other terminal was in contact with the earth, a current passed through the galvanometer. For determining the strength of this current I proposed to called a micro-ampere the 10-9part of an ampere. At the height of about 100 meters in the average the current begins to be regular, and increases at the height of 300 meters to 4,000 or 5,000 of these units. The increase is very regular, and seems to be a linear function of the height. I have, nevertheless, found the smallest quantities of dust contained in the atmosphere or the lightest veil of cirrus disturbed the measurement very materially, and generally made the potential lower. In negative experiments of this nature I have made at Breslau, at the Sohneekoppe, and at the "Reisengebirge," especially at the last station, an increase of potential was observed, not only by reason of the perpendicular height, but also by reaching such regions of the atmosphere as were situated horizontally to about 200 meters from the utmost steep of the same mountain, Sohneekoppe. Therefore it must, according to Mr. Exner, be assumed that the surface of the air presents a surface of equal potential, and that the falling surfaces of high potential were stretched parallel over the plane contours of the air, and more thinly or narrow lying over all the elevated points, as, for example, mountains, church towers, etc. On the basis of these facts I think it easy to explain the electricity of thunder storm clouds, in fact every cloud, or every part of a cloud, may be considered as a leading conductor, such clouds as have for the most part perpendicular height. After being induced the change results by supposing the conduction of electricity either from the upper or from the lower side, according to greater or smaller speed of the air in the height. In the first case the clouds will be charged positive, in the other negative. I am inclined, therefore, to state that the electricity of thunder storm clouds must be considered as a special but disturbed case of the normal electric state of the atmosphere, and that all attempts to explain thunder storm electricity must be based on the study of the normal electric state of the atmosphere.
[1]
Abstract of a paper read before the British Association meeting at Manchester, September, 1887.
Abstract of a paper read before the British Association meeting at Manchester, September, 1887.
At intervals in the history of science, long periods of comparative inertia have attended the death of its more distinguished workers. As time progresses and the number of workers increases, there is a corresponding increase in the number of men whose labors merit distinction in the literature of every language; but as these accessions necessitate in most cases further division of the honors, many names conspicuously identified with modern science fail of their just relative rank, and fade into unmerited obscurity. Thus the earlier workers in science, like Scheele, Liebig, Humboldt, and others of that and later periods, have won imperishable fame, to which we all delight to pay homage, while others of more recent times, whose contributions have perhaps been equally valuable for their respective periods, are given stinted recognition of their services, if indeed their names are not quite forgotten. Nothing illustrates so clearly the steps in the evolution of science as a review of the relative status of its representatives. As in the political history of the world an epoch like that of the French revolution stands out like a mountain peak, so in the history of science an epoch occurs rather by evolution than revolution, when a hitherto chaotic, heterogeneous mass of knowledge is rapidly given shape and systematized. Previous to the seventeenth century an immense mass of facts had accumulated through the labors of investigators working under the Baconian philosophy, but these facts had been thrown together in a confused, unsystematic manner. A man of master mind was then needed to grasp the wonders of nature and formulate the existing knowledge of them into a scientific system with a natural basis. Such a system was given by Linnæus, and so great were its merits that it continues the foundation of all existing systems of classification.
Charles Linnæus was born May 13, 1707, in a country place named Roshult in Smaland, near Skane, Sweden. He was called Charles after the well known Swedish knight errant, King Charles XII., then at the height of his renown.
The natural beauty of his native place, with its verdure-clad hills, its stately trees, and sparkling brooks fringed with mosses and flowers, inspired the boy Linnæus with a love of nature and a devotion to her teachings which tinged the current of his whole life. He was destined by his parents for the ministry, and in accordance with their wish was sent to the Vexio Academy ("gymnasium"). Here the dull theological studies interfered so much with his study of nature that he would have felt lost but for the sympathy of Dr. Rothman, one of his teachers, a graduate of Harderwyk University, Holland, who had been a pupil of Boerhaave (the most eminent physician and scientist of his day), and been much impressed by his scientific teachings.
Portrair of Linnaeus
Dr. Rothman took a great interest in Linnæus, and assured his father that he would prove a great success financially and otherwise as a physician (an occupation whose duties then included a study of all existing sciences). The father was satisfied, but dreaded the effect the announcement of such a career would have on the mother, whose ambition had been to see her son's name among the long list of clergymen of the family who had been ministers to the neighboring church of Stentrohult. She finally yielded, and the best possible use was made by Linnæus of Dr. Rothman's tuition. Latin, then the mother tongue of all scientists and scholars, he wrote and spoke fluently.
At the age of twenty Linnæus entered the University of Lund, and remained there a year. Here he formed the acquaintance of a medical man, a teacher in the university, who opened his home and his library to him, and took him on his botanical excursions and professional visits. Some time later, on Dr. Rothman's advice, Linnæus entered the University of Upsala, then the most celebrated university of Northern Europe. His parents were able to spare him but one hundred silver thalers for his expenses. At the end of a year his money was spent, his clothing and shoes were worn out, and he was without prospects of obtaining a scholarship. When things were at their gloomiest he accidentally entered into a discussion with a stranger in the botanical garden, who turned out to be a clergyman scientist named Celsius. Celsius, while staying at Upsala, had conceived the plan of given a botanical description of biblical plants. Having learned that Linnæus had a herbarium of 600 plants, he took the young man under his protection, and opened up to him his home and library.
While studying in this library, his observations regarding the sexes in plants, hitherto in a chaotic state, took form, stimulated by an abstract published in a German journal of Vaillant's views, and before the end of 1729 the basis of the sexual system had appeared in manuscript. This treatise having been seen by a member of the university faculty, Linnæus was invited to fill a temporary vacancy, and lectured with great success therein one and a half years. Meanwhile the foundation of the celebrated treatises afterward published on the sexual system of classification and on plant nomenclature had been laid.
As in the history of most great men, a seemingly great misfortune proved to be a turning point in his career. The position he had temporarily filled with such credit to himself and profit to the students was claimed by its regular occupant, and, despite the opposition of the faculty, Linnæus had to relinquish it. The two subsequent years were spent in botanical investigations under the patronage of various eminent men. During one of these he traveled through Lapland to the shores of the Polar Sea, and the results of this expedition were embodied in his "Lapland Flora," the first flora founded on the sexual system. He delivered a peripatetic course of lectures, and during one of these he formed the acquaintance of Dr. Moræus, a pupil of the great Boerhaave. Dr. Moræus took Linnæus into partnership with him. Here again a seeming misfortune proved to be a great advantage. Linnæus fell in love with the eldest daughter of Dr. Moræus, but was denied her hand until he should graduate in medicine. Linnæus, to complete his studies as a physician, then entered the University of Harderwyk, Holland, the alma mater of his first benefactor, Dr. Rothman, and of the great Boerhaave.
After two years' study he was graduated in medicine with high honors. His thesis, "The Cause of Chills," received special commendation. He visited all the botanical gardens and other scientific institutions for which Holland was then renowned. A learned and wealthy burgomaster, Gronovius, having read his "Systema Naturæ" in manuscript, not only defrayed the cost of its publication, but secured him the high honor of an interview with the great Boerhaave—an honor for which even the Czar Peter the Great had to beg.
Boerhaave's interest was at once awakened, and he gave Linnæus so strong a recommendation to Dr. Burman, of Amsterdam, that the influence of the scientific circles of the Dutch metropolis was exerted in behalf of Linnæus, and he was soon offered the position of physician superintendent of a magnificent botanical garden owned by a millionaire horticultural enthusiast, Clifford, a director of the Dutch East India Company. Linnæus' financial and scientific future was now secure. Publication of his works was insured, and his position afforded him every opportunity for botanical research. After five years' residence in Holland, during which he declined several positions of trust, he determined to return to Sweden. His fame had become so widespread in Western Europe that his system was already adopted by scientists and made the basis of lectures at the Dutch universities. In the French metropolis he was greatly esteemed, and during a visit thereto he was a highly distinguished guest.
ROSHULT, SWEDEN, BIRTHPLACE OF LINNÆUS.ROSHULT, SWEDEN, BIRTHPLACE OF LINNÆUS.
His reception in Sweden was rather frigid, and but for the hearty welcome by his family and betrothed he would probably have returned to Holland. Hisamour proprewas also doubtless wounded, and he determined to remain and fight his way into the magic circle of the gilt-edged aristocracy which then monopolized all scientific honors in Stockholm and the universities. He acquired a great reputation for the treatment of lung disease, and was popularly credited with the ability to cure consumption. This reached the ears of the queen (a sufferer from the disease), who directed one of her councilors to send for Linnæus. He soon recognized the name of Linnæus as one of great renown on the Continent, and at once took him under his protection.
The star of Linnæus was now in the ascendant. He was soon delegated to various pleasant duties, among which was the delivery of lectures on botany and mineralogy in the "auditorium illustre" at Stockholm. He at this time founded the "Swedish Scientific Academy," and was its first president. In 1741 he was elected professor of medicine in Upsala University, which chair he exchanged for that of botany and the position of director of the botanical garden. This opened up a new era for science in Sweden. He who was regarded as the world's greatest botanist abroad had at last been similarly acknowledged in his native land.
With the indomitable courage and tact characteristic of the man, he set on foot a gigantic scientific popular educational project. The government, under his direction, established a system of exploring expeditions into the fauna, flora, and mineralogy of the whole Swedish peninsula, partly for the purpose of developing the resources of the country, partly in the interest of science, but more especially to interest the mass of the people in scientific research. The vast majority of the people of Sweden, like those of other countries, were dominated by fetichic superstitions and absurd notions about plants and vegetables, which were indorsed to a certain extent by popular handbooks devoted more to the dissemination of marvels than facts. A popular clergyman, for instance, stated in a description of the maritime provinces that "certain ducks grew upon trees." The vast stride which was made by the populace in the knowledge of nature was due to these efforts of Linnæus, who, in order to further popularize science, established and edited, in conjunction with Salvius, a journal devoted to the discussion of natural history.
During this period, on the first of May, semi-weekly excursions were made from the university, the public being invited to attend. The people came to these excursions by hundreds, and all classes were represented in them—physicians, apothecaries, preachers, merchants, and mechanics, all joined the procession, which left the university at seven in the morning, to return at eve laden with zoological, botanical, and mineralogical specimens.
A man who could thus arouse popular enthusiasm for science a century and a half ago must have been a remarkable genius. Trusted students of Linnæus were sent on botanical exploring expeditions throughout the world. The high renown in which Linnæus was held was shown in the significant title, almost universally bestowed upon him, of "The Flower King."—Western Druggist.
[1]
For the illustrations and many facts in the life of Linnæus we are indebted to theIllustrated Tidning, Stockholm.
For the illustrations and many facts in the life of Linnæus we are indebted to theIllustrated Tidning, Stockholm.
The first actual attempt to make the wave length of sodium light a standard of length was made by Peirce.1This method involves two distinct measurements: first, that of the angular displacement of the image of a slit by a diffraction grating, and, second, that of the distance between the lines of the grating. Both of these are subject to errors due to changes of temperature and to instrumental errors. The results of this work have not as yet been published; but it is not probable that the degree of accuracy attained is much greater than one part in fifty or a hundred thousand. More recently, Mr. Bell, of the Johns Hopkins University, using Rowland's gratings, has made a determination of the length of the wave of sodium light which is claimed to be accurate to one two hundred thousandth part2. If this claim is justified, it is probably very near the limit of accuracy of which the method admits. A short time before this, another method was proposed by Mace de Lepinay.3This consists in the calculation of the number of wave lengths between two surfaces of a cube of quartz. Besides the spectroscopic observations of Talbot's fringes, the method involves the measurement of the index of refraction and of the density of quartz, and it is not surprising that the degree of accuracy attained was only one in fifty thousand.
Several years ago, a method suggested itself which seemed likely to furnish results much more accurate than either of the foregoing, and some preliminary experiments made in June have confirmed the anticipation. The apparatus for observing the interference phenomena is the same as that used in the experiments on the relative motion of the earth and the luminiferous ether.
Light from the source ats(Fig. 1), a sodium flame, falls on the plane parallel glass,a, and is divided, part going to the plane mirror,c, and part to the plane mirror,b. These two pencils are returned alongcaeandbae, and the interference of the two is observed in the telescope ate. If the distances,acandab, are made equal, the plane,c, made parallel with that of the image ofb, and the compensating glass,d, interposed, the interference is at once seen. If the adjustment be exact, the whole field will be dark, since one pencil experiences external reflection and the other internal.
If nowbbe moved parallel with itself a measured distance by means of the micrometer screw, the number of alternations of light and darkness is exactly twice the number of wave lengths in the measured distance. Thus the determination consists absolutely of a measurement of a length and the counting of a number.
The degree of accuracy depends on the number of wave lengths which it is possible to count. Fizeau was unable to observe interference when the difference of path amounted to 50,000 wave lengths. It seemed probable that with a smaller density of sodium vapor this number might be increased, and the experiment was tried with metallic sodium in an exhausted tube provided with aluminum electrodes. It was found possible to increase this number to more than 200,000. Now it is very easy to estimate tenths or even twentieths of a wave length, which implies that it is possible to find the number of wave lengths in a given fixed distance between two planes with an error less than one part in two millions and probably one in ten millions. But the distance corresponding to 400,000 wave lengths is roughly a decimeter, and this cannot be determined or reproduced more accurately than say to one part in 500,000. So it would be necessary to increase this distance. This can be done by using the same instrument together with a comparer.
The intermediate standard decimeter,lm(Fig. 2), is put in place of the mirror,b. It consists of a prism of glass one decimeter long with one end,l, plane, and the other slightly convex, so that when it touches the plane,m, Newton's rings appear, and these serve to control any change in the distance, lm, which has been previously determined in wave lengths.
The end,l, is now adjusted so that colored fringes appear in white light. These can be measured to within one-twentieth of a wave length, and probably to within one-fiftieth. The piece,lm, is then moved forward till the fringes again appear atm. Then the refractometer is moved in the same direction till the fringes appear again atl, and so on till the whole meter has been stepped off. Supposing that in this operation the error in the setting of the fringes is always in the same direction, the whole error in stepping off the meter would be one part in two millions. By repetition this could of course be reduced. A microscope rigidly attached to the carriage holding the piece, lm, would serve to compare, and a diamond attached to the same piece would be used to produce copies. All measurements would be made with the apparatus surrounded by melting ice, so that no temperature corrections would be required.
Probably there would be considerable difficulty in actually counting 400,000 wave lengths, but this can be avoided by first counting the wave lengths and fractions in a length of one millimeter and using this to step off a centimeter. This will give the nearest whole number of wave-lengths, and the fractions may be observed directly. The centimeter is then used in the same way to step off a decimeter, which again determines the nearest whole number, the fraction being observed directly as before.
The fractions are determined as follows: The fringes observed in the refractometer under the conditions above mentioned can readily be shown to be concentric circles. The center has the minimum intensity when the difference in the distances,ab,ac, is an exact number of wave lengths. The diameters of the consecutive circles vary as the square roots of the corresponding number of waves. Therefore, ifxis the fraction of a wave length to be determined, andythe diameter of the first dark ring,dbeing the diameter of the ring corresponding to one wave length, thenx=y2/d2.
There is a slight difficulty to be noted in consequence of the fact that there are two series of waves in sodium light. The result of this superposition of these is that as the difference of path increases, the interference becomes less distinct and finally disappears, reappears, and has a maximum of distinctness again, when the difference of path is an exact multiple of both wave lengths. Thus there is an alternation of distinct interference fringes with uniform illumination. If the length to be measured, the centimeter for instance, is such that the interference does not fall exactly at the maximum—to one side by, say, one-tenth the distance between two maxima, there would be an error of one-twentieth of a wave length requiring an arithmetical correction.
Among other substances tried in the preliminary experiments were thallium, lithium, and hydrogen. All of these gave interference up to fifty to one hundred thousand wave lengths, and could therefore all be used as checks on the determination with sodium. It may be noted that in case of the red hydrogen line, the interference phenomena disappeared at about 15,000 wave lengths, and again at about 45,000 wave lengths; so that the red hydrogen line must be a double line with the components about one-sixtieth as distant as the sodium lines.—Amer. Jour. Science.
[1]
Nature, xx, 99, 1879; this Journal, III, xviii, 51, 1879.
Nature, xx, 99, 1879; this Journal, III, xviii, 51, 1879.
[2]
On the absolute wave lengths of light, this Journal, III, xxxiii, 167, 1887.
On the absolute wave lengths of light, this Journal, III, xxxiii, 167, 1887.
[3]
Comptes Rendus, cii, 1153, 1886; Journal, de Phys., II, v, 411, 1886.
Comptes Rendus, cii, 1153, 1886; Journal, de Phys., II, v, 411, 1886.
[RURAL NEW YORKER]
Upon this subject I am able to speak with the freedom habitually enjoyed by some voluminous agricultural writers—my imagination will not be hampered by my knowledge.
In debatable climates, like Ohio, Illinois, Kansas and southward, it is conceded that a great point would be gained by the discovery of some plan—not too expensive—that would make it safe to put away potatoes in the summer, as soon as ripe, so that they would go through the winter without sprouting and preserve their eating qualities till potatoes come again. As it is, digging must be deferred till late, for fear of rot; the fields of early varieties grow up with weeds after they are "laid by." In the spring a long interregnum is left between old potatoes fit to eat and the new crop, and the seed stock of the country loses much of its vigor through sprouting in cellars and pits. Most farmers have had occasion to notice the difference between the yield from crisp, unsprouted seed potatoes and that from the wilted, sprouted tubers so often used. Some years ago Professor Beal made a test of this difference. I speak from recollection, but think I am right in saying that, according to the published account which I saw, he found one sprouting of seed potatoes lowered the yield 10 per cent.; each additional sprouting still further reduced the crop, till finally there was no yield at all. Even a 10 per cent. shrinkagein all that portion of the annual potato crop grown from sprouted seed would result in an aggregate loss of millions of bushels. The question how to store potatoes and not have them sprout I have seen answered in the papers by recommending a "cold" cellar, of about 40 degrees temperature. If there are cellars that are cold in warm weather, without the use of some artificial process, I have not seen them. The temperature of well water is about 45 degrees only, and anybody knows how much colder a well is than a cellar. But the greatest difficulty comes in from the fact that potatoes are such a prolific source of heat in themselves.
If a 40 degree cellar could be found and be filled with potatoes, the temperature would at once begin to rise, and the later in the season, the faster it would go up. I repeat that a cellar filled with potatoes will have a much higher temperature than the same cellar would have if empty. This I have learned as Nimbus learned tobacco growing—"by 'sposure." I hope I won't be asked "why." I don't know. The reason is unimportant. The remedy is the thing. The only help for it that I know of is to give the cellar plenty of ventilation, put the potatoes in as clean as possible, and then shovel them over every month or two. This will keep the sprouting tendency in check very largely; but it won't make it practicable to begin storing potatoes in July or cause them to keep in good flavor till June.
Several years ago I placed some barrels of early Ohio potatoes in the Kansas City cold storage warehouses from March till July. They were kept in a temperature of 38 degrees, and came out crisp and very little sprouted. The plan of this structure was very simple: a three-story brick building so lined with matched lumber and tarred paper as to make three air-spaces around the wall. In the top story was a great bulk of ice, which was freely accessible to the air that, when cooled, passed through ducts to the different "cool rooms." The results were satisfactory, but the system seemed too expensive for potatoes. I have wondered whether it was necessary for potatoes to be kept as cold as 38 degrees. Would not a current of air passing through pipes showered with well water keep them cold enough? Wine vaults, I believe, are sometimes cooled by air currents forced through a cold water spray. If the air blast of well water temperature would be sufficient, the apparatus for producing it would be comparatively inexpensive—or at least much cheaper than those plans of cold storage where ice is stored in quantity over the cool room. However, any process that could be devised would probably be unprofitable to the small cropper, and the larger the business done, the less the cost per bushel. If it should be found that individual operators could not reach such an improvement on a profitable scale, why could not several of them pool their issues sufficiently to build, jointly, a potato elevator? There are at least 50,000 bushels of potatoes held in store by farmers within three miles of where I live. It seems to me there would be many advantages and economies in having that large stock under one roof, one insurance, one management; on a side track where they could be loaded in any weather or state of the roads, besides the great item that the temperature could be controlled, by artificial means, in one large building much cheaper than in several small ones.
EDWIN TAYLOR.
Edwardsville, Kans.
[KNOWLEDGE.]
The figure illustrating this article is taken fromL'Astronomie, and represents the remarkable southern comet of January, 1887, as drawn on successive days by Mr. Finlay, of Cape Town.
The comet was first seen by a farmer and a fisherman of Blauwberg, near Cape Town, on the night of January 18-19. The same night it was seen at the Cordoba Observatory by M. Thome. On the next Mr. Todd discovered it independently at the Adelaide Observatory, and watched it till the 27th. On the 22d Mr. Finlay detected the comet, and was able to watch it till the 29th. At Rio de Janeiro M. Cruls observed it from the 23d to the 25th; and at Windsor, New South Wales, Mr. Tebbutt observed the comet on the 28th and 30th. Moonlight interfered with further observations.
The comet's appearance was remarkable. Its tail, long and straight, extended over an arc of 30 degrees, but there was no appreciable condensation which could be called the comet's head. The long train of light, described as nearly equal in brightness to the Magellanic clouds, seemed to be simply cut off at that end where in most comets a nucleus and coma are shown.
This comet has helped to throw light on one of the most perplexing puzzles which those most perplexing of all the heavenly bodies, comets, have presented to astronomers.
In the year 1668 a comet was seen in the southern skies which attracted very little notice at the time, and would probably have been little thought of since had not attention been directed to it by the appearance and behavior of certain comets seen during the last half century. Visible for about three weeks, and discovered after it had already passed the point of its nearest approach to the sun, the comet of 1668 was not observed so satisfactorily that its orbit could be precisely determined. In fact, two entirely different orbits would satisfy the observations fairly, though one only could be regarded as satisfying them well.
This orbit, however, was so remarkable that astronomers were led to prefer the other, less satisfactory though it was, in explaining the observed motions of the comet. For the orbit which best explained the comet's movements carried the comet so close to the sun as actually to graze his visible surface.
Moreover, there was this remarkable, and, indeed, absolutely unique peculiarity about the orbit thus assigned: the comet (whose period of revolution was to be measured by hundreds of years) actually passed through the whole of that part of its course during which it was north of our earth's orbit plane in less than two hours and a half! though this part of its course is a half circuit around the sun, so far as direction (not distance of travel) is concerned. That comet, when at its nearest to the sun, was traveling at the rate of about 330 miles per second. It passed through regions near the sun's surface commonly supposed to be occupied by atmospheric matter.
Now, had the comet been so far checked in its swift rush through those regions as to lose one thousandth part of its velocity, it would have returned in less than a year. But the way in which the comet retreated showed that nothing of this sort was to be expected. I am not aware, indeed, that any anticipations were ever suggested in regard to the return of the comet of 1668 to our neighborhood. It was not till the time of Halley's comet, 1682, that modern astronomy began to consider the question of the possibly periodic character of cometic motions with attention. (For my own part, I reject as altogether improbable the statement of Seneca that the ancient Chaldean astronomers could calculate the return of comets.) The comet of 1680, called Newton's, was the very first whose orbital motions were dealt with on the principles of Newtonian astronomy, and Halley's was the first whose periodic character was recognized.
In 1843 another comet came up from the south, and presently returned thither. It was, indeed, only seen during its return, having, like the comet of 1668, been only discovered a day or two after perihelion passage. Astronomers soon began to notice a curious resemblance between the orbits of the two comets. Remembering the comparative roughness of the observations made in 1668, it may be said that the two comets moved in the same orbit, so far as could be judged from observation. The comet of 1843 came along a path inclined at apparently the same angle to the earth's orbit plane, crossed that plane ascendingly at appreciably the same point, swept round in about two hours and a half that part of its angular circuit which lay north of the earth's orbit plane, and, crossing that plane descendingly at the same point as the comet of 1668, passed along appreciably the same course toward the southern stellar regions! The close resemblance of two paths, each so strikingly remarkable in itself, could not well be regarded as a mere accidental coincidence.