[1]The lecture was illustrated by about fifty views on the screen, which cannot be reproduced here, showing photographs of mills and mechanical drawings of the methods of construction alluded to in the lecture.
[1]
The lecture was illustrated by about fifty views on the screen, which cannot be reproduced here, showing photographs of mills and mechanical drawings of the methods of construction alluded to in the lecture.
The lecture was illustrated by about fifty views on the screen, which cannot be reproduced here, showing photographs of mills and mechanical drawings of the methods of construction alluded to in the lecture.
It is clearly intimated by Mr. Hanssen, in his determination of the mechanical equivalent of heat, published in theScientific American Supplement, No. 642, April 21, 1888, that his object is to determine theabsolutevalue of this constant. With his data he finds it to be 771.89 foot pounds. But the determination by direct experiment gives a larger value. Thus, the most reliable experiments—those of Joule and Rowland—give values exceeding by several units that found by Hanssen. A committee of the British Association, appointed for this purpose, reported in 1876 that sixty of the most reliable of Joule's experiments gave the mean value 774.1. The experiments were made with water at a temperature of about 60° F., according to the mercurial thermometer, and reduced to its value at the temperature of melting ice, according to the formula given by Regnault for the variation of the specific heat of water at varying temperature under the constant pressure of one atmosphere. According to this formula the specific heat of water increases with the temperature above the melting point of ice, so that the equivalent would be somewhat less at 32° F. than at 60° F. It will be found in Regnault'sRelation des Experiencesthat he experimented on water at high temperatures, but more recently Professor Rowland has found that the specific heat of water isgreaterat 40° F. than at 60° F., thus reversing between these limits the law given by Regnault; the increase, as given by the most probable values, being, roughly, about1/250of its value at 60° F. The proper correction due to this cause would make the equivalent over 777 foot pounds, instead of 774.1. Professor Rowland's experiments, when reduced to the same thermometer, same temperature, and same latitude as Joule's, agreed very nearly with those of the latter, being about1/1000part larger; so that the chief difference in the ultimate values consists in the reductions for temperature and latitude. The force of gravity being less for the lower latitudes, the number representing the mechanical equivalent will be greater for the latter, since the unit pound mass must fall through a greater number of feet to equal the same work; so that the equivalent will be greater at Paris than at Manchester. Professor Rowland also found that the degrees on the air thermometer from 40° F. upward to above 60° F. exceeded those on the mercurial thermometer throughout the corresponding range, and that from 40° to 41° the degree was between1/150and1/200of a degree larger on the air thermometer than on the mercurial. Although this fraction is too small to be observed by ordinary means, yet, if it exists, it cannot be ignored if absolute values are sought. Regnault employed the air thermometer in his experiments, while Joule used the mercurial thermometer, and if Joule's value 774.1 be increased by1/200of itself in order to reduce it from the equivalent of the degree on the mercurial thermometer to that on the air thermometer, we get 778 foot pounds, nearly. Rowland found from his experiments that when reduced to the air thermometer and to the latitude of Baltimore, the equivalent was nearly 783, subject to small residual errors.
Nearly all writers upon this subject—except Rankine—have considered that the mechanical equivalent of heat, in British units, was the energy necessary to raise the temperature of one pound of water from 32° F. to 33° F., but Rankine defines it as the heat necessary to increase the temperature of one pound of water one degree Fahrenheit from that of maximum density, or from 39° F. to 40° F. For ordinary practice it is immaterial which of these definitions is used, for the errors resulting therefrom are much less than those resulting from ordinary observations. But when the value is to be determined by direct experiment at the standard temperature, Rankine's limits are much to be preferred; for it is so very difficult to determine exact values by observation when the substance is near the state bordering on a change of state of aggregation, as that of changing from water to ice. Observations made at about 60° F. were reduced by means of Regnault's law for the specific heat of water, as has been stated, which is expressed by the formula
c=1+4—105t+9—107t2
in whichtdenotes the temperature according to the Centigrade scale. According to this law, the mechanical equivalent would not be 0.2 of a foot pound greater at 5° C. (41° F.) than at 0° C. (32° F.); hence, if this law were correct, it would make no practical difference whether the temperature were at 0° C. or 5° C. This law makes thecomputedvalue at 32° F. about 0.95 of a foot pound less than that determined by experiment at 60° F.; whereas Rowland's experiments make itgreaterat 40° F. by more than four foot pounds, for the air thermometer. In determining afixedvalue to be used for scientific purposes, it is necessary to fix the place, the thermometer, and the particular degree on the thermometer. The place may be known by its latitude if reduced to the level of the sea. The air thermometer agrees most nearly with that of the ideally perfect gas thermometer, while the mercurial thermometer differs very much from it in some cases. Thus, Regnault found that when the air thermometer indicated 630° F. above the melting point of ice (or 662° F.), the mercurial thermometer indicated 651.9° above the same point (683.9° F.), a difference of 22° F. It is apparent that the air thermometer furnishes the best standard. As for the particular degree on the scale to be used for the standard, it is apparent, from the observations above made, that the temperature corresponding to that at or near the maximum density of water is more desirable than that at the melting point of ice. The fact, also, that the specific heats at constant pressure and at constant volume are the same at the point of maximum density, as shown by theory, is an additional argument in favor of selecting this point for the standard. It thus appears that the solution of this problem, which appears simple and very definite by Mr. Hanssen's method, becomes intricate and, to a limited degree, indeterminate when subjected to the refinements of direct experiment. If the constants used by Hanssen are absolutely correct, then his result must be unquestioned; but since physical constants are subject to certain residual errors, one would as soon think of finding the specific heat of air at constant volume, by using the value of the mechanical equivalent as one of the elements, and trusting the result, as he would to trust to the computed value of the mechanical equivalent without subjecting it to the test of a direct experiment. We will, therefore, examine the constants used to see if they are the exact values of the quantities they represent.
He says they are universally accepted as correct; and this may be true, when used for general purposes, and yet not be scientifically exact. He uses 0.2377 as the specific heat of air. This is the value, to four decimals, found by Regnault. Thus, Regnault gives for the mean value of the specific heat of air
Between —30° Cand +10° C.0.23771" 0° C"100° C.0.23741" 0° C"200° C.0.23751
And we know of no reason why one of these values should be used rather than another, except that the mean of a large range of temperatures may be more nearly correct than that of any other; and if this reason determines our choice, the number 0.2375 would be used instead of 0.2377. Although this difference is small, yet the former value would have reduced his result about 0.7 of a foot pound.
Again, he uses 0.1686 for the specific heat of air at constant volume. The value of this constant has never been found to any degree of accuracy by direct experiment, and we are still dependent upon the method established by La Place and Poisson, according to which the constant ratio of the specific heat of a gas at constant pressure to that at constant volume is found by means of the velocity of sound in the gas. The value of the ratio for air, as found in the days of La Place, was 1.41, and we have 0.2377 ÷ 1.41 = 0.1686, the value used by Clausius, Hanssen, and many others. But this ratio is not definitely known. Rankine in his later writings used 1.408, and Tait in a recent work gives 1.404, while some experiments give less than 1.4, and others more than 1.41.
An error of one foot in a thousand in determining the velocity of sound will affect the third decimal figure one or two units. A small difference in the assumed weight of a cubic foot of air also affects the result. M. Hanssen gives 0.080743 pound as the weight at 32° F. under the pressure of one atmosphere; while Rankine gives 0.080728 pound. In my own computations I use 1.406 as a more probable value of the constant sought. This will give for the specific heat of air at constant pressure
0.2375 ÷ 1.406 = 0.1689
This is only 0.0003 of a unit greater than the value used by Hanssen, but it would have given him nearly 775, instead of 771.89.
Again, he uses 491.4° F. for the absolute temperature of melting ice. The exact value of this constant is unknown; but the mean value as determined by Joule and Thomson, in their celebrated experiments with porous plugs, was 492.66° F. This value would slightly change his result. It will be seen from the above that a small change in the constants used may affect by several units the computed value of the mechanical equivalent. I have computed it, using 1.406 for the ratio of the specific heat of air at constant pressure to that at constant volume, 491.13° F. as the temperature of melting ice above the zero of theairthermometer, 26,214 feet for the height of a homogeneous atmosphere, and 0.2375 for the specific heat of air, and I find, by means of these constants, 778. If computed from the zero of the absolute scale, 492.66° F., I find 777 to the nearest integer. Recently I have used 778. If the value given by Rowland, about 783 according to the air thermometer at 39° F., should prove to be correct, it seems probable that the constant 1.406 used above would be reduced to about 1.403, or that the other constants must be changed by a small amount. The height of the homogeneous atmosphere used above, 26,214 feet, is the value used by Rankine as deduced from Regnault's figures, and only one foot less than the value used by Sir William Thomson; but the figures used by Mr. Hanssen give 26,210½ feet.
The method above called Hanssen's is really that of Dr. Mayer (the German professor), who in 1842 used it for determining the mechanical equivalent; but on account of erroneous data, the value found by him was much too small.
The author described a series of economy trials, non-condensing, made with one of his central valve triple expansion engines, with one crank, having three cylinders in line. By removing one or both of the upper pistons, the engine could be easily changed into a compound or into a simple engine at pleasure. Distinct groups of trials were thus carried out under conditions very favorable to a satisfactory comparison of results.
No jackets were used, and no addition had, therefore, to be made to the figures given for feed water consumption on that account. Most of the trials were conducted by the author, but check trials were made by Mr. MacFarlane Gray, Prof. Kennedy, Mr. Druitt Halpin, Professor Unwin, and Mr. Wilson Hartnell. The work theoretically due from a given quantity of steam at given pressure, exhausting into the atmosphere, was first considered.
By a formula deduced from the θ φ diagram of Mr. MacFarlane Gray, which agreed in results with the less simple formulas of Rankine and Clausius, the pound weight of steam of various pressures required theoretically per indicated horse power were ascertained. (See annexed table.)
A description was then given of the main series of trials, all at four hundred revolutions per minute, of the appliances used, and of the means taken to insure accuracy. A few of the results were embodied in the table. The missing quantity of feed water at cut off, which, in the simple trials, rose from 11.7 per cent. at 40 lb. absolute pressure to nearly 30 per cent. at 110 lb. and at 90 lb. was 24.8 per cent., was at 90 lb. only 5 per cent. in the compound trials. In the latter, at 160 lb., it increased to17 per cent., but, on repeating the trial with triple expansion, it fell to 5.46 per cent. or to 4.43 per cent. in another trial not included in the table.
On the other hand, from the greater loss in passages, etc., the compound engine must always give a smaller diagram, considered with reference to the steam present at cut-off, than a simple engine, and a triple a smaller diagram than a compound engine. Nevertheless, even at 80 lb. absolute pressure, the compound engine had considerable advantage, not only from lessened initial condensation, but from smaller loss from clearances, and from reducing both the amount of leakage and the loss resulting from it. These gains became more apparent with increasing wear. The greater surface in a compound engine had not the injurious effect sometimes attributed to it, and the author showed how much less the theoretical diagram was reduced by the two small areas taken out of it in a compound engine than by the single large area abstracted in a simple engine. The trials completely confirmed the view that the compound engine owed its superiority to reduced range of temperature. At the unavoidably restricted pressures of the triple trials, the losses due to the new set of passages, etc., almost neutralized the saving in initial condensation, but with increased pressure—say to 200 lb. absolute—there would evidently be considerable economy. The figures of these trials showed that the loss of pressure due to passages was far greater with high than with low pressure steam, and that pipes and passages should be proportioned with reference to the weight of steam passing, and not for a particular velocity merely.
The author described a series of calorimetric tests upon a large scale (usually with over two tons of water), the results of which were stated to be very consistent. After comparing the dates of initial condensation in cases where the density of steam, the area of exposed surface, and the range of temperature were all variables, with other cases (1) where the density was constant and (2) where the surface was constant, the author concluded that, at four hundred revolutions per minute, the amount of initial condensation depended chiefly on the range of temperature in the cylinder, and not upon the density of the steam or upon the extent of surface, and that its cause was probably the alternate heating and cooling of a small body of water retained in the cylinder. The effect of water, intentionally introduced into the air cushion cylinder, corroborated the author's views, and he showed how small a quantity of water retained in the cylinder would account for the effects observed. At lower speeds surface might have more influence. The favorable economical effect of high rotative speed,per se, was very apparent.
In a trial with a compound engine, with 130 lb. absolute pressure, the missing quantity at cut-off rose from 11.7 per cent. at 405 revolutions to 29.66 per cent. at 130 revolutions, the consumption of feed water increasing from 20.35 lb. to 23.67 lb. This saving of 14 per cent. was due solely to increase of speed. Similar trials had been made with a simple engine. In one simple trial at slow speed the missing quantity rose to 44.5 per cent. of the whole feed water.
Intended mean admission pressure (Lb.)4090110130150160170Simple, Compound, or Triple.S.S.C.S.C.C.C.T.C.T.T.Actual mean admission pressure (Lb.)40.8892.6587.54106.3109.3130.6149.9151.9158.5158.1172.5Percentage ratio of actual mean pressure,referred to low pressure piston,to theoretical mean pressure98.210091.3100.794.894.294.684.5495.985.385.2Indicated horse power16.5131.6128.1433.53336.3138.5935.6939.5535.5638.45Feed water actually used per indicated H.P.H.—Simple (Lb.)Compound (Lb.)Triple (Lb.)42.7626.89...26...........................34.16...21.3720.3519.45...19.19...........................19.68...19.1918.45Steam required theoretically per 1 H.P.H. (Lb.)34.6719.2419.8617.917.6516.2515.2315.1614.8714.914.36Percentage efficiency81.171.582.268.882.58078.37777.477.677.8Percentage of feed water missing at cut off in high pressure cylinder.....................5.33...6.845.01Ditto high pressure cylinder......5...9.511.715.114.841712.0615.33Ditto low pressure cylinder11.724.815.229.5616.2519.120.622.1221.322.1124.21Percentage of feed water missing at end of stroke in low pressure cylinder10.418.8314.2521.5316.5917.5520.6918.0119.5518.8119.25
The author compared a series of compound trials, at different powers, with 130 lb. absolute pressure, and various ratios of expansion, with a series giving approximately the same powers at a constant ratio of expansion, but with varying pressures, being practically a trial of automatic expansion against throttling. Starting with 40 indicated horse power, 130 lb. absolute pressure, four expansions, and a consumption of 20.75 lb. of water, the plan of varying the expansion, as compared with throttling, showed a gain of about 7 per cent. at 30 indicated horse power, but of a very small percentage when below half power. If the engine had an ordinary slide valve, the greater friction, added to irregular motion, would probably neutralize the saving, while if the engine were one in which initial condensation assumed more usual proportions, the gain would be probably on the side of variable pressure. Even as it was, the diagrams showed that the missing quantity became enormously large as the expansion increased. Judging only by the feed water accounted for by the indicator, the automatic engine appeared greatly the more economical, but actual measurement of the feed water disproved this. The position of the automatic engine was, however, relatively more favorable when simple than when compound.
In conclusion, the author referred to a trial with a condensing engine, at 170 lb. absolute pressure, in which the feed water used was 15.1 lb., a result evidently capable of further improvement, and to an efficiency trial of a combined central valve engine and Siemens' dynamo, made for the Admiralty, at various powers. At the highest power the ratio of external electrical horse power to indicated horse power in the engine was 82.3 per cent. Taking the thermo-dynamic efficiency of the engine at 80 per cent., that of the combined apparatus would be nearly 66 per cent.
[1]Abstract of paper read before the Institution of Civil Engineers, March 13.
[1]
Abstract of paper read before the Institution of Civil Engineers, March 13.
Abstract of paper read before the Institution of Civil Engineers, March 13.
The subject of our large illustration this week is a large steel bridge carrying the Central Pacific Railway over the St. Lawrence River at Lachine, near Montreal. The main features of this really magnificent structure are the two great channel spans, each 408 feet long. It will be noticed that the design combines, in a very ingenious manner, an upper and a lower deck structure, the railway track being laid on the top of the girders forming the side spans, and on the lower flanges of the channel spans, which are crossed by continuous girders, 75 feet deep, over the central pier, and supported by brackets as shown. The upper of our two engravings shows the method of constructing the principal spans, which were built outward from the side piers, while the work on the center pier was extended on each side to meet. It was built at the works of the Dominion Bridge Company, Montreal, from the design of Mr. C. Shaler Smith, the well-known American bridge engineer.—Engineering.
Railway Bridge at Lachine.
While the last few years have seen great advances made in the designs of steamships and of their engines, little or nothing has been done in the way of improving the screw propeller. As a general rule it would appear to be taken for granted that no radical improvement could be made in the form of the propeller, although various metals have been introduced in its manufacture with the view of increasing its efficiency. For sea-going steamers, however, the shape remains the same, the variation chiefly relating to the number of blades employed. A striking departure from ordinary practice, however, has of late been made by Mr. B. Dickinson, who has invented a screw propeller which, on practical trial, has given an efficiency far in advance of the ordinary screw. This new propeller we illustrate here in Figs. C and D, while Fig. A shows an ordinary propeller. The Dickinson propeller illustrated has six blades, giving a surface of 30 square feet; it is right handed, and has pitch of 15 ft. and a diameter of 10 ft. 6 in. The ordinary screw propeller shown at Fig. A is right handed and two bladed, with a pitch at the boss of 13 ft. 6 in. and at the tip of 15 ft. It has a diameter of 10 ft. 9 in. and 32 square ft. of surface. The projected area looking forward is 22 square ft. and the projected area looking athwartship 22.84 square feet. The most graphic way of illustrating the principle of Mr. Dickinson's propeller is to take a two bladed propeller of the ordinary type as shown at Fig. A in the annexed cuts, and divide into three sections as in Fig. B, then move section No. 1 to the line position on the shaft of No. 3, and No. 3 to that of No. 1, No. 2 remaining stationary. The effect of this interchange will be that (having regard to the circle of rotation) No. 3, the rearmost section, will rotate in advance of No. 2, and No. 2 in advance of No. 1 (see Fig. C). By this arrangement the water operated on escapes freely astern from every blade—that from No. 1 passing in the wake of No. 2, while that from Nos. 2 and 1 passes in the wake of No. 3. Fig. D represents the blades with a wider spread as practically used. The advantages claimed by Mr. Dickinson for his propeller, and which are sufficiently important to be given in detail, are:
Figs. A-D.Figs.A-D.
1. That the blades of each section, when the vessel is in motion, necessarily cut solid, undisturbed water, each blade operating upon precisely the same quantity of water as an individual broad blade would do, though, of course, it parts with it in one-third of the time.
2. That each sectional blade exerts the equivalent efficiency of the first or entering third portion of the breadth of an ordinary propeller blade, and that consequently the combined sections have greater effective power. It is now regarded by experts as an ascertained fact that the after or trailing portion of the broad blade is relatively non-effective as compared with the forward or entering portion.
3. When three blades are fitted, the spent water from No. 2 being delivered immediately in the wake of No. 3, and that from No. 1 in the wake of No. 2, has the effect of destroying or reducing to a minimum the back draught of sections Nos. 2 and 3, No. 1 alone being subject to this drawback. This is of greater importance than might at first thought appear, as in cases where there are three or four blades revolving in one plane, the water is drawn after the retreating blade, lessening the resistance to the face of the advancing one.
4. That by the subdivision of the blades, as arranged spirally, the water passing through within the radius of the propeller has its resisting capacity more thoroughly worked out than is possible with any propeller whose blades are all on the same plane. This view is confirmed by the visibly increased rotation of the water in the wake of the vessel.
5. That by broadening the blades or increasing the number of sections, the diameter of the propeller may be proportionately diminished without the sacrifice of engine power. This is often desirable with vessels of light draught, the complete immersion of the screw being at all times necessary to avoid waste of power.
6. The propeller being made and fitted on the shaft in sections, all that is necessary in case of accident is to replace the broken section. This in many cases could be done afloat.
7. The blades being arranged to take their water at different planes, there is the greater certainty of one or other of the sections operating upon what is termed the water of friction. This is considered an advantage.
8. Where it is desirable, the blades of the different sections can be made of varying breadth or pitch.
9. The principle of division into two or more sections applies equally to two, three, or four bladed ordinary propellers.
10. The adoption of this principle does not entail any alteration or enlargement of the screw space or bay as usually provided.
11. As a consequence of the freedom and rapidity with which the water operated upon escapes from the narrow blades, the depression at the stern of the vessel caused by the action of the ordinary propeller is greatly reduced.
12. The vibration caused by this propeller is so slight as to be hardly noticeable, thereby effecting a saving in the wear and tear of the engine and machinery. This may also be a consideration in promoting the comfort of passengers.
From a practical and working point of view we take Mr. Dickinson's chief claims to be, in the first place, the yielding of a greater speed per power employed, or an economy in obtaining an equal speed; in the second, increased, rapidity in maneuvering and stopping a vessel; and in the third, a reduction of vibration. In order to put these claims to a practical and reliable comparative test, Messrs. Weatherley, Mead & Hussey, of Saint Dunstan's Hill, London, placed at the inventor's disposal two of their new steamers, the Herongate and the Belle of Dunkerque. These are in every respect sister boats, and were built in 1887 by Messrs. Short Brothers, and engined by Mr. John Dickinson, of Sunderland. The Herongate was fitted about four months ago with the largest propeller yet made on Mr. B. Dickinson's principle, the Belle of Dunkerque having an ordinary four-bladed propeller of the latest improved type. Every precaution was taken to place the two vessels on the same footing for the purpose of a comparative test, which was recently carried out. Both vessels previously to the trial were placed on the gridiron, cleaned and painted, their boilers opened out and scaled, their steam gauges independently tested, and both vessels loaded with a similar cargo of pitch, the only difference being that the Herongate carried 11 tons more dead weight and had one inch more mean draught than the Belle of Dunkerque, while the former had been running continuously for nine months against the latter's two and a half months. On the day of the trial the vessels were lying in the Lower Hope reach, and it was decided to run them over the measured mile there with equal pressure of steam. The order of running having been arranged, the Herongate got under way first, the Belle of Dunkerque following over the same course. Steaming down against tide, the Herongate is said to have come round with remarkable ease and rapidity, and in turning on either helm, whether with or against tide, to have shown a decided advantage. Equally manifest, it is stated, was the superiority shown in bringing up the vessel by reversing, when running at full speed, thus confirming the very favorable reports previously received by the owners from their captains since the Dickinson propeller was fitted to the Herongate. Those who were on board her state that the vibration was scarcely noticeable. From a statement submitted to us it is clear that the Herongate had the turn of the scale against her in dead weight and draught, vacuum, and diagrams taken, but notwithstanding (making allowance for one faulty run due to the variations in tide) she appears to have more than held her own in the matter of speed, with a saving of 4½ and 3¼ revolutions per minute at 140 lb. and 160 lb. steam pressure respectively. This is further confirmed by the results of a run made after the experiments were concluded, the two vessels being placed in line, and fairly started for a half hour's run over the flood with 150 lb. steam pressure. At the expiration of that time the Herongate was judged to be leading by at least half a length, her revolutions being 76, as against 80 in the Belle of Dunkerque. It was agreed by all present at these trials that the propeller had realized in full the three main working advantages claimed for it. This being the first Dickinson propeller fitted to a sea-going vessel of this size, it is quite within the limits of possibility that the present results may be improved upon in further practice. In any case we can but regard this propeller as a distinct and original departure in marine propulsion, and we congratulate Mr. Dickinson on his present success and promising future. Messrs. Weatherley, Mead & Hussey also deserve credit for their discernment, and for the spirited manner in which they have taken up Mr. Dickinson's ingenious invention. We understand that they are so satisfied with the results that they intend having one of their larger ocean-going steamers fitted with the Dickinson propeller.—Iron.
IMPROVED DOBBY.IMPROVED DOBBY.
At the Manchester Royal Jubilee Exhibition, Messrs. Butterworth & Dickinson, Burnley, showed Catlow's patent dobby, which is illustrated above, as applied to a strong calico loom. This dobby is a double lift one, thus obtaining a wide shed, and the use of two lattice barrels connected by gearing so that they both revolve in the same direction. The jack lever is attached to the vertical levers, the top and bottom catches being worked respectively by the two barrels, and connected with the ends of the levers. To each of these catches a light blade spring is attached, which insures them being sprung upon the top of the knife, and thereby obtaining a certain lift. A series of wooden jacks or levers are employed, so as to give a varyinglift to the front and back healds, in this way keeping the yarn in even tension, and preventing slack sheds. The healds are drawn down by means of a series of levers adjoining one another, and worked by means of a rocking bar driven from the tappet shaft. When the shed is being formed, the jacks are pushed down until it is fully open, and the warp is thus drawn down with the same certainty as the upward movement is made.—Industries.
Sulphur, or brimstone, is a hard, brittle substance of various colors, from brilliant yellow to dark brown, without smell when cool, of a mild taste, and burns with a pale blue flame, emitting pungent and suffocating fumes. Its specific gravity is from 1.9 to 2.1.
Sulphur exists more or less in all known countries, but the island of Sicily, it is thought, is the only place where it is produced on a large scale, and consequently that island appears to command the market. Small quantities have been found in the north of Italy, the Grecian Archipelago, Russia, Austria, Poland, France, Spain, eastern shores of Egypt, Tunis, Iceland, Brazil, Central America, and the United States. Large quantities are said to exist in various countries of Asia, but it is understood to be impracticable to utilize the same, consequent upon the distance from any commercial port and the absence of rail or other roads.
Sulphur is of two kinds, one of which is of volcanic emanation, the other being closely allied to sedimentary rocks. The latter is found in Sicily, on the southern and central portions of the island. Mount Etna, situated in the east, seems to exert no influence in the formation of brimstone. There are various hypotheses relative to its natural formation. Dr. Philip Swarzenburg attributes it to the emanations of sulphur vapor expelled from metallic matter existing in the earth, consequent upon the fire in the latter, while Professors Hoffman and Bischoff ascribe it to the decomposition of sulphureted hydrogen. Hoffman believes the sulphureted hydrogen must have passed through the fissures of stratified rocks, but Bischoff is of opinion that the sulphureted hydrogen must have been the result of the decomposition of sulphate of lime in the presence of organic matter. The theory of others is that sulphur owes its origin to the combination of lacustrine deposits with vegetable matter, and others again suppose that it is due to the action of the sea upon animal remains. The huge banks of rock salt often met with in the vicinity of sulphur mines, and which in some places stretch for a distance of several miles, seem to indicate that the sea has worked its way into the subsoil. Fish and insects, which are frequently found in strata of tripoli, which lie under sulphur beds, induce the belief that lakes formerly existed in Sicily.
The following is a list of the various strata which form part of the crust of the earth in Sicily, according to Professor Mottura, an Italian geologist:
Pliocene.—Sandstone; coarse calcareous rock; marl.
Upper Miocene.—Calcareous marl; gypsum, etc.; sulphur embedded in calcareous limestone; silicious limestone; tripoli, containing fossils of fish, insects' eggs, etc.
Middle Miocene.—Sandstone containing quartz, intercalated with marl of a saltish taste.
Lower Miocene.—Rock salt; blue marl, containing petroleum and bitumen; flintstone; ferruginous clay, mixed with aragonite and bituminous schists; ferruginous and silicious sandstone.
Eocene.—Limestone, containing diaspores and shells.
At times one or another of the strata disappears, while the order of some is slightly reversed on account of the broken state of the crust. Upon the whole, however, the above has been generally observed in the various mines by the author referred to.
Sulphur mines have been operated in Sicily over three hundred years, but until the year 1820 its exportation was confined to narrow limits. At present the number of mines existing in Sicily is about three hundred, nearly two hundred of which, being operated on credit, are, it is understood, destined to an early demise. It is said that there are about 30,000,000 tons of sulphur in Sicily at present, and that the annual production amounts to about 400,000 tons. If this should be true, taking the foregoing as a basis, the supply will become exhausted in about seventy-five years.
In 1819 a law was passed in Italy, which is still in force, governing mining in Sicily, which provides that should a land owner discover ore in his property he would be the owner thereof, and should have the right to mine, operate, or rent the property to others for that purpose, but if he should decline to operate his mines or to rent them to others to be operated, the state would rent them on its own account.
Royalties vary from 12 to 45 per cent. They are paid according to the quality of the ore and the facilities for producing sulphur; 25 per cent. may, however, be taken as an average. There is a land tax of 36 per cent. of the net income, which is usually paid by the owners and lessees of the mines, in proportion to the quantity of sulphur which they produce. The export duty is 10 lire per ton. All mines are inspected by government officials once a year, and the owners are required to furnish the state with plans of the works and their progress, with a view to insure the safety of the workmen and to ascertain the extent of the property.
Those who rent their mines receive from 10 to 40 per cent. of the sulphur produced. Leases are valid for such period as the contracting parties may stipulate therein. The general limit, however, is nine years. The average lease is 25 per cent., 40 per cent. being paid only when the mines are very favorably situated and the production good. Some lessees prefer paying a considerable sum in cash in advance, at the beginning of the term of the lease, and giving 15 or 20 per cent. in sulphur annually thereafter, instead of a higher percentage.
The external indications of the presence of sulphur are the appearance of gypsum and sulphurous springs. These are indubitable signs of the presence of sulphur, and when discovered the process resorted to here, in order to reach the sulphur, is to bore a hole sufficiently large to admit a man, after which steps are constructed in the passage in order to facilitate the workmen in going to and fro. These steps extend across the passage, and are about 25 centimeters high and 35 broad. The inclination of the holes or passages varies from 30 to 50 degrees. Upon attaining the depth of several meters water is often met with, and in such considerable quantity that it is impossible to proceed. Hence it becomes necessary to either pump the water out or retreat in order to bore elsewhere. It is often necessary to bore several passages in order to discover the ore or seam of sulphur. When, however, it has been discovered the passages are made to follow its direction, whether upward or downward. As the direction of seams is in most cases irregular, that of the passages or galleries is likewise. Where the ore is rich and the matrix yielding, the miners break it by means of pick-axes and pikes, but when such is not the case gunpowder is resorted to, the ore in this case being carried to the surface by boys. The miners detach the ore from the surrounding material, and the cavities which ensue in consequence assume the appearance of vast caves, which are here and there supported by pillars of rock and ore in order to keep them from falling or giving way. In order to strengthen the galleries sterile rock is piled upon each side and cemented with gypsum. In extensive mines, however, these supports and linings are too weak, and not infrequently, as a result, the galleries and caverns give way, occasionally causing considerable havoc among the miners. Sulphur is found from the surface to a depth of 150 meters. The difficulties met with in operating mines are numerous, and among the greatest in this category are water, land slides, irregularity of seam, deleterious gases, hardness of rocks and matrices. Of these difficulties, water is the most frequently met with. Indeed, it is always present, and renders the constant use of pumps necessary. At one time miners were allowed to dig where they pleased so long as sulphur was extracted, the consequence being that in groups of mines, the extent and direction of which being unknown to their respective owners, one mine often fell into or upon another, thus causing destruction to life and property. It was largely for this reason, it is understood, that the government determined to require owners and lessees of mines to furnish plans thereof to proper authority, and directed that official inspection of the mines should be made at stated periods. In order to comply with the decree of the government it became necessary to employ mining engineers to draw the plans, etc., and those employed were generally foreigners. In the system of excavation described no steam power is employed. Pumping is performed by means of primitive wooden hand pumps, and when sufficient ore has been collected it is conveyed on the backs of boys to the surface—a slow, costly, and difficult procedure. This system may, however, be suitable to small mines, but in large mines there is no economy in hand labor; indeed, much is lost in time and expense by it. For this reason steam has been introduced into the larger and more important mines. The machinery employed is a hoisting apparatus, with a drum, around which a coil is wound, with the object of hoisting and lowering trucks in vertical shafts. Steam pumps serve to extract the water. The force of the hoisting apparatus varies from 15 to 50 horse power. The fuel consumed is English and French coal, the former being preferred, as it engenders greater heat. The cost of a ton of coal at the wharf is $4.40, whereas in the interior of the island it costs about $10. The shafts or pits are made in the ordinary way, great care being taken in lining them with masonry in order to guard against land slides. In level portions of the country vertical shafts are preferred, but where the mine is situated upon a hill a debouch may often be found below the sulphur seam, when an inclined plane is preferred, the ore being placed in trucks and allowed to run down the plane on rails until it reaches the exterior of the mine, where it suddenly and violently stops, and as a result the trucks are emptied of their load, when they are drawn up the plane to be refilled; and thus the process goes on indefinitely. In these mines a gutter is made in the inclined plane which carries off the water, thus dispensing with the necessity of a pump and the requisites to operate it. The galleries and inclined shafts are lined with beams of pine or larch, which are brought hither from Sardinia, as Sicily possesses very little timber. The mines are illuminated by means of iron oil lamps, the wicks of which are exposed. The lamps are imported from Germany. In certain cases an earthenware lamp, made on the island, and said to be a facsimile of those used by the Phœnicians, is employed. This lamp is made in the shape of a small bowl. It is filled with oil and a wick inserted, which hangs or extends outward, and is thus ignited, the flame being exposed to the air. Safety lamps are unknown, and those described are generally secure. Few explosions take place—only when confined carbonic hydrogen is met with in considerable quantities, and when the ventilation is not good. In this case the mine is easily ignited, and once on fire may burn for years. The only practical expedient for extinguishing the fire is to close all inlets and outlets in order to shut off the air. This, however, is difficult and takes time. Notwithstanding the closing of communications, the gases escape through the fissures and openings which obtain everywhere, and the ingress of air makes it next to impossible to extinguish the fire; hence it burns indefinitely or until the mine is exhausted. Occasionally the burning of a mine results beneficially to its owners, in that it dispenses with the necessity of smelting, and produces natural, refined sulphur.
Galleries in extent are usually 1.20 by 1.80 meters, and when ore is not found and it becomes necessary to extend the galleries, laborers are paid in accordance with the progress they may make and the character of the rock, earth, etc., through which it may be necessary to cut, as follows:
Silicious limestone, 60 lire per meter; daily progress, 0.20 meter.
Gypsum, 50 lire per meter; daily progress, 0.30 meter.
Marl, 30 lire per meter; daily progress, 0.50 meter.
Clay, 15 lire per meter; daily progress, 1 meter.
Laborers working in the ore are paid 4.30 lire per ton. This includes digging, extracting, and illumination. In some mines, however, the laborers are paid when the sulphur is fused and ready for exportation. One ton of sulphur, or its equivalent (say from 40 to 50 lire), is the amount generally paid. In mines where this system obtains the administration is only responsible for their maintenance. Each miner produces on an average about 1½ tons of ore daily, and when the works are not more than 40 meters in depth he employs one boy to assist him, two boys when they reach 60 meters, and three when under 100 meters. These boys are from seven to sixteen years of age, and are paid from 0.85 to 1.50 lire per day by the miner who employs them. They carry from 1,000 to 1,500 pounds of ore daily, or in from six to eight hours. The food consumed by miners is very meager, and consists of bread, oil, wine, or water; occasionally cheese, macaroni, and vegetables are added to the above.
Mining laborers generally can neither read nor write, and when employed in mines distant from habitations or towns, live and sleep therein, or in the open air, depending on the season or the weather. In a few mines the laborers are, however, provided with suitable dwelling places, and a relief fund is in existence for the succor of the families of those who die in the service. This fund is greatly opposed by the miners, from whose wages from 1 to 2 per cent. is deducted for its maintenance. In the absence of a fund of this character, the sick or infirm are abandoned by their companions and left to die. Generally miners are inoffensive when fairly dealt with. They are said to be indolent and dishonest as a rule. The managers of mines receive from 3,000 to 5,000 lire per annum; chief miners from 1,500 to 2,500 lire; surveyors, 700 to 1,000 lire; and weighers and clerks, from 1,000 to 2,000 lire per annum. The total number of mining laborers in Sicily is estimated at about 25,000.
The ore for fusion of the first grade as to yield contains from 20 to 25 per cent. of sulphur, that of the second grade from 15 to 20 per cent., and of the third grade 10 to 15 per cent. The usual means adopted for extracting sulphur from the ore is heat, which attains the height of 400 degrees Centigrade, smelting with the kiln, which in Sicilian dialect is called a "calcarone." The "calcarone" is capable of smelting several thousand tons of ore at a time and is operated in the open air. Part of the sulphur is burned in the process of smelting in order to liquefy the remainder. "Calcaroni" are situated as closely to the mouth of a shaft as possible, and if practicable on the side of a hill, in order that when the process of smelting is complete, the sulphur may run down the hill in channels prepared for the purpose. The shop of a "calcarone" is circular and the floor has an inclination of from 10 to 15 degrees. A design of a "calcarone" is herewith inclosed. The circular wall is made of rude stone work, cemented together with gypsum. The thickness of the wall at the back is 0.50 meter, and from this it gradually becomes thicker until in front, where it is 1 meter, when the diameter is to be 10 meters. In front of the thickest part of the wall an opening is left, measuring 1.20 meters high and 0.25 meter broad.
Through this opening the liquid sulphur flows. Upon each side of this opening two walls are built at right angles with the circular wall, in order to strengthen the front of the kiln. These walls are 80 centimeters thick each and are roofed. A door is hinged to these walls, thus forming a small room in front of each kiln in which the keeper thereof resides from the commencement to the termination of the flow of sulphur. The inclined floor of the kiln is made of stone work and is covered with "ginesi," the name given to the refuse of a former process of smelting. The stone work is 20 centimeters thick, and the "ginesi" covering 25 centimeters, which gradually becomes thicker as it approaches its lowest extremity. The front part of the circular wall is 3.50 meters high and the back 1.80 meters. The interior of the wall is plastered with gypsum in order to render it impermeable.
The cost of a "calcarone" of about 500 tons capacity is 800 lire. The capacity varies from 40 to 5,000 tons, or more, depending upon circumstances. If a mine is enabled to smelt the whole year round, the smaller "calcaroni," being more easily managed, are preferred; the inverse is the case as to the larger "calcaroni," when this is impracticable. When a "calcarone" is situated within 100 meters of a cereal farm, its operation is prohibited by law during the summer, lest the fumes of the sulphur should destroy the crop.
When, however, the distance is greater from the farm or farms than 100 meters, smelting is permitted; but should any damage ensue to the crops as a result of the fumes, the owners of the "calcaroni" are required to liquidate it. Therefore the mines which are favorably situated smelt the entire year, and employ "calcaroni" of from 40 to 500 tons, as there is less risk of a process failing, which occasionally happens, and for the reason that the ore can be smelted as soon as it is extracted; whereas, when kilns or "calcaroni" are situated within or adjacent to the limit adverted to, they can only be operated five or six months in the year, consequent upon which the ore is necessarily stacked up all through the summer or until such time as smelting may be commenced without endangering the crops, when it becomes necessary to use "calcaroni" whose capacity amounts to several thousand tons. As intimated, these large "calcaroni" are not so manageable as those of smaller dimensions, and as a result many thousands of tons of sulphur are lost in the process of smelting, besides perhaps the loss of an entire year in labor. Again, the ore deteriorates or depreciates when long exposed to the air and rain, all of which, when practicable, render the kilns or "calcaroni" of the smaller capacity more advantageous and lucrative to those operating sulphur mines in Sicily. Smelting with a "calcarone" of 200 tons capacity consumes thirty days, one of 800 tons 60 days, and with a "calcarone" of 2,000 tons capacity from 90 to 120 days are consumed.
In loading or filling the "calcaroni," the larger blocks of ore are placed at the bottom as well as against the mouth, in order to keep the lower part of the kiln as cool as possible with a view of preventing the liquid sulphur from becoming ignited as it passes down to where it makes its exit, etc. The blocks of ore thus first placed in position are, for obvious reasons, the most sterile. After the foundation is thoroughly laid the building of the "pile" is proceeded with, the larger blocks being placed in the center to form, as it were, the backbone of the pile; the smaller blocks of ore are arranged on the outside of these and in the interstices. The shape or form of the pile when completed is similar to a truncated cone, and when burning the kiln looks like a small volcano. When the kiln has been filled with ore, the whole is covered with ginesi with a view of preventing the escape of the fumes. The ore is then ignited by means of bundles of straw, impregnated or saturated with sulphur, beingheld above the thin portion of the top of the kiln, which is at once closed with ginesi, and the "calcarone" is left to itself for about a week. During the burning process the flames gradually descend, and the sulphur contained in the ore is melted by the heat from above. In about seven or eight days sulphuric fumes and sublimed sulphur commence to escape, when it becomes necessary to add a new coat of ginesi to the covering and thus prevent the destruction of vegetation by the sulphur fumes. The mouth of the kiln, which has been left open in order to create a draught, is closed up about this time with gypsum plaster. When the sulphur is all liquefied it finds its way to the most depressed part of the kiln, and there, upon encountering the large sterile blocks, quite cold, already referred to, solidifies. It is again liquefied by means of burning straw, whereupon an iron trough is inserted into a mouth made in the kiln for the purpose, and the reliquefied sulphur runs into it, from which it is immediately collected into wooden moulds, called "gadite," and which have been kept cool by being submerged in water. Upon its becoming thoroughly cool the sulphur is taken out of the moulds referred to, and is now in solid blocks, each weighing about 100 weight. Two of these blocks constitute a load for a mule, and cost from 4 to 5 francs.
The above is the result when the operation succeeds; but this is not always the case. At times the sulphur becomes solidified before it reaches the mouth of the kiln, because of the heat not being sufficient to keep it liquid in its passage thereto, and other misfortunes not within control, and consequent upon the use of the larger kilns, or "calcaroni."
When the sulphur ceases to run from the kiln, the process is complete. The residue is left to cool, which consumes from one to two months. The cooling process could be accomplished in much less time by permitting the air to enter the kiln, but this would be destructive to vegetation, and even to life, consequent upon the fumes of the sulphur. The greatest heat at a given time in a kiln is calculated to be above 650 degrees Centigrade—that is, at the close of the process. This enormous heat is generally allowed to waste, whereas it is understood it could be utilized in many ways. A gentleman of the name of Gill is understood to have invented a recuperative kiln, which will, if generally adopted, utilize the heat of former processes named. A ton of ore containing about 25 per cent. of sulphur yields 300 pounds of sulphur. This is considered a good yield. When it yields 200 pounds it is considered medium, and poor when only 75 pounds. Laborers are paid 0.40 lire per ton for loading and unloading kilns, and from thirty to forty hands are employed at a time. The keeper of a kiln receives from 2 to 2.50 lire per day.
Notwithstanding the "calcarone" has many defects, it is the simplest and cheapest mode of smelting, and is preferred here to any other system requiring machinery and skilled labor to operate it.
The following are the principal furnaces in use here: Durand's; Hirzel; Gill and Kayser's system of fusion; Conby Bollman process; Thomas steam process of smelting; and Robert Gill's recuperative kilns.
There are seven qualities or grades of sulphur, viz.:
1. Sulphur almost chemically pure, of a very bright and yellow color.
Second Best.—Slightly inferior to the first quality; bright and yellow.
Second Good.—Contains 4 to 5 per cent. of earthy matter, but is of a bright yellow.
Second Current.—Dirty yellow, containing more earthy matter than that last named.
Third Best.—Brownish yellow; this tint depends on the amount of bitumen which it contains.
Third Good.—Light brown, containing much extraneous matter.
Third Current.—Brown and coarse.
These qualities are decided by color, not by test. The difference of price is from 3 to 10 francs per ton. Manufacturers prefer the third best, because of its containing more sulphuric acid and costing less than the sulphur of better quality.
Sulphur is conveyed to the seaboard by rail, in carts, or on mules or donkeys. Conveyance by cart, mule, or donkey is only resorted to when the distance is short or from mines to railroad stations. The tariff in the latter case is understood to be 1 lire per ton per mile. The railroad tariff is 0.12 per ton per kilometer; but it is contemplated, it is understood, to reduce this to 7 centimes in a short time. The price per ton of sulphur is as follows: