38 Proceedings of the Royal Society. bits; with an introductory Account of the Telescopic Apparatus that has been used on this occasion, and a final Exposition of some calculated Particulars deduced from the Observations. By William Herschel, LL.D. An Account of some Experiments with a large Voltaic Battery. By J. G. Children, esq. On the Dispersive Power of the At mosphere, and its Effect on Astronomical Observations. By Stephen Lee. Deterinination of the North Polar Distances, and proper Motion of Thirty Fixed Stars. By John Pond, esq. astronomer royal. An Essay towards the Calculus of Functions. By C. Babbage, esq. Some additional Experiments and Observations on the Relation which subsists between the Nervous and Sanguiferous Systems. By A. P. Wilson Philip. At the anniversary meeting of this Society on the 30th of November, the President and Council adjudged the gold medal given by Sir Godfrey Copley, to Dr. DAVID BREWSTER, for his experiments and discoveries on light and heat contained in his papers in the Philosophical Transactions. The destructive accidents from the explosion of inflammable gases in collieries, which we, in common with all the friends of humanity, have lately had such frequent occasion to deplore, have recently induced several distinguished scientific men to turn their attention to the discovery of a method of lighting those subterranean recesses without endangering the lives of the workmen. Various contrivances for this purpose have been devised, but none has been found to answer the end desired so completely as the lamp invented by the illustrious Sir HUMPHRY DAVY, whose paper on this subject, read before the Royal Society on the 9th November, appears of such importance to all persons employed or interested in mines, that we shall give it entire. On the Fire-damp of Coal-Mines, and on Methods of Lighting the Mines so as to prevent its Explosion. By Sir H. DAVY. The accidents arising from the explosion of the fire-damp or inflammable gas of coalmines, mixed with atmospherical air, are annually becoming more frequent and more destructive in the collieries in the north of England. A committee has been for some time formed at Sunderland, for the benevolent [Feb. 1, purpose of investigating the causes of these accidents, and of searching for means of preventing them. In consequence of an invitation from the Rev. Dr. Gray, one of the most active members of this committee, I was induced to turn my attention to the subject. I went to the north of England, and visited some of the principal collieries in the neighbourhood of Newcastle, for the purpose of ascertaining the condition of the workings, and the state of their ventilation. I found the greatest desire to assist my inquiries in the gentlemen acquainted with the northern collieries, as well as in the inspectors or viewers of the mines: and I have particular obligations on this point to the Rev. Dr. Gray, Cuthbert Ellison, esq. M. P., the Rev. John Hodgson, Mr. Buddle, and Mr. Dunn. Dr. Fenwick, Dr. Clanny, and Mr. Fenwick, likewise kindly offered me their assistance. From the information which I collected on the spot, increased by the perusal of a Report of Mr. Buddle on the state of the mines, I was convinced that, as far as ventilation was concerned, the resources of modern science had been fully employed; and that a mode of preventing accidents was only to be sought for in a method of lighting the mines free from danger, and which, by indicating the state of the air in the part of the mine where inflammable air was disengaged, so as to render the atmosphere explosive, should oblige the miners to retire till the workings were properly cleared. An account of an ingenious apparatus for burning a candle, supplied with atmospheri cal air by a bellows through water, has been published in the Philosophical Transactions, by Dr. Clanny; but I believe this apparatus has not yet been used in any of the collieries. The common means employed for lighting those parts of the mine where danger is steel wheel, which being made to revolve in apprehended from the fire-damp, is by a contact with flint, affords a succession of sparks: but this apparatus always requires a person to work it; and, though much less liable to explode the fire-damp than a common candle, yet it is said to be not entirely free from danger. Mr. Buddle having obligingly shown to me the degree of light required for working the collieries, I made several experiments, with the hope of producing such a degree of light, without active inflammation; I tried Kunckel's, Canton's, and Baldwin's phosphorus, and likewise the electrical light in close vessels, but without success; and even had these degrees of light been sufficient, the processes for obtaining them, I found, would be too complicated and difficult for the miners. The fire-damp has been shown by Dr. Henry, in a very ingenious paper published in the nineteenth volume of Nicholson's Journal, to be light carburetted hydrogen gas, 1816.] Sir H. Davy on preventing Explosions in Coal Mines. and Dr. Thomson has made some experiments upon it; but the degree of its combustibility, as compared with that of other inflammable gases, has not, I believe, been examined, nor have many different specimens of it been analyzed; and it appeared to me, that some minute chemical experiments on its properties ought to be the preliminary steps to inquiries respecting methods of preventing its explosion. I therefore procured various specimens of the firedamp in its purest state, and made a number of experiments upon it. And in examining its relations to combustion, I was so fortunate as to discover some properties belonging to it, which appear to lead to very simple methods of lighting the mines, without danger to the miners, and which, I hope, will supply the desideratum so long anxiously required by humanity. The fire-damp is produced in small quantities in coal-mines, during the common process of working. The Rev.Mr.Hodgson informed me, that on pounding some common Newcastle coal fresh from the mine in a cask furnished with a small aperture, the gas from the aperture was inflammable. And on breaking some large lumps of coal under water, I ascertained that they gave off inflammable gas. Gas is likewise disengaged from bituminous-schist, when it is worked. The great sources of the fire-damp in This is probably owing to the coal strata having been formed under a pressure greater than that of the atmosphere, so that they give off elastic fluid when they are exposed to the free atmosphere: and probably coals containing animal remains evolve not only the fire-damp, but likewise azote and carbonic acid, as in the instance of the gas sent by Dr. Clanny In the Apennines, near Pietra Mala, I examined a fire produced by gaseous matter, constantly disengaged from a schist stratum : and from the results of the combustion, I have no doubt that it was pure fire-damp. Mr. M. Faraday, who accompanied me, and assisted me in my chemical experiments, in my journey, collected some gas from a cavity in the earth, about a mile from Pietra Mala, then filled with water, and which, from the quantity of gas disengaged, is called Aqua Buja. I analysed it in the Grand Duke's laboratory at Florence, and found that it was pure light hydro-carbonate, requiring two volumes of oxygen for its combustion, and producing a volume of carbonic acid gas. It is very probable that these gases are disengaged from coal strata beneath the surface, er from bituminous schist above coal; and at some future period new sources of riches may be opened to Tuscany from this invaluable mineral treasure, the use of which, in this country, has supplied such extraordinary resources to industry. 39 mines are, however, what are called blowers, or fissures in the broken strata, near dykes, from which currents of fire-damp issue in considerable quantity, and sometimes for a long course of years.* When old workings are broken into, likewise, they are often found filled with fire-damp; and the deeper the mine the more common in general is this substance. I have analyzed several specimens of the fire-damp in the laboratory of the Royal Institution; the pure inflammable part was the same in all of them, but it was sometimes mixed with small quantities of atmospherical air, and in some instances with azote and carbonic acid. Of six specimens collected by Mr. Dunn from a blower in the Hepburn colliery, by emptying bottles of water close to it, the purest contained one-fifteenth only of atmospherical air, with no other contamination, and the most impure contained five-twelfths of atmospherical air; so that this air was probably derived from the circumambient air of the mine. The weight of the purest specimen was for 100 cubical inches 19.5 grains. One measure of it required for its complete combustion by the electric spark nearly two measures of oxygen, and they formed nearly one measure of carbonic acid. Sulphur heated strongly, and repeatedly sublimed in a portion of it freed from oxygen by phosphorus, produced a considerable enlargement of its volume, sulphuretted hydrogen was formed, and charcoal precipitated; and it was found that the volume of the sulphuretted hydrogen produced, when it was absorbed by solution of potassa, was exactly double that of the fire-damp decomposed. It did not act upon chlorine in the cold; but, when an electric spark was passed through a mixture of one part of it with two of chlorine, there was an explosion, with a diminution to less than one-fourth, and much charcoal was deposited. The analysis of specimens of gas sent to my friend John George Children, esq. by Dr. Clanny, afforded me similar results; but they contained variable quantities of carbonic acid gas and azote. Different specimens of these gases were tried by the test of exposure to chlorine both in darkness and light: they exhibited no marks of the presence of olefiant gas or hydrogen; and the residuum produced by detonation with chlorine showed them to be free from carbonic oxide. It is evident, then, that the opinion formed by other chemists respecting the fire damp is perfectly correct; and that it is the same substance as the inflammable gas of marshes, Sir James Lowther found a uniform current produced in one of his mines for two years and nine months. Phil, Trans, vol. xxxviii, p. 112. 40 Sir H. Davy on preventing Explosions in Coal Mines. [Feb. 1, the exact chemical nature of which was first demonstrated by Mr. Dalton; and that it consists, according to my view of definite proportions, of 4 proportions of hydrogen in weight 4, and one proportion of charcoal in weight 11.5. I made several experiments on the combustibility and explosive nature of the firedamp. When 1 part of fire-damp was mixed with 1 of air, they burnt by the approach of a lighted taper, but did not explode; 2 of air and 3 of air to 1 of gas produced similar results. When 4 of air and 1 of gas were exposed to a lighted candle, the mixture being in the quantity of 6 or 7 cubical inches in a narrow-necked bottle, a flame descended through the mixture, but there was no noise: 1 part of gas, inflamed with 6 parts of air in a similar bottle, produced a slight whistling sound: 1 part of gas with 8 parts of air rather a louder sound: 1 part with 10, 11, 12, 13, and 14 parts, still inflamed, but the violence of combustion diminished. In 1 part of gas and 15 parts of air, the candle burst without explosion with a greatly enlarged flame and the effect of enlarging the flame, but in a gradually diminishing ratio, was produced as far as 30 parts of air to 1 of gas. The mixture which seemed to possess the greatest explosive power, was that of 7 or 8 parts of air to 1 of gas; but the report produced by 50 cubical inches of this mixture was less than that produced by one-tenth of the quantity of a mixture of 2 parts of atmospherical air and 1 of hydrogen. It was very important to ascertain the degree of heat required to explode the firedamp mixed with its proper proportion of air. I found that a common electrical spark would not explode 5 parts of air and 1 of fire-damp, though it exploded 6 parts of air and I of damp: but very strong sparks from the discharge of a Leyden jar seemed to have the same power of exploding different mixtures of the gas as the flame of the taper. Well-burned charcoal, ignited to the strongest red heat, did not explode any mixture of air and of the fire-damp; and a fire made of well-burned charcoal, i. e. charcoal that burned without flame, was blown up to whiteness by an explosive mixture containing the fire-damp, without producing its inflammation. An iron rod at the highest degree of red heat, and at the common degree of white heat, di not inflame explosive mixtures of the fire-damp; but, when in brilliant combustion, it produced the effect. The flame of gaseous oxide of carbon as well as of olefiant gas exploded the mixtures of the fire-damp. In respect of combustibility, then, the fire-d differs most materially from the other common inflammable gases. Olefiant gas, which I have found explodes mixed in the same proportion with air, is fired by קני. both charcoal and iron heated to dull redness. Gaseous oxide of carbon, which explodes whenmixed with 2 parts of air, is likewise inflammable by red-hot iron and charcoal. And hydrogen, which explodes when mixed with three-sevenths of its volume of air, takes fire at the lowest visible heat of iron and charcoal; and the case is the same with sulphuretted hydrogen. I endeavoured to ascertain the degree of expansion of mixtures of fire-damp and air during their explosion, and likewise their power of communicating flaine through apertures to other explosive mixtures. I found that when 6 of air and 1 of firedamp were exploded over water by a strong electrical spark, the explosion was not very strong, and, at the moment of the greatest expansion, the volume of the gas did not appear to be increased more than one-half. In exploding a mixture of 1 part of gas from the distillation of coal, and 8 parts of air in a tube of a quarter of an inch in diameter and a foot long, more than a second was required before the flame reached from one end of the tube to the other; and I could not make any mixture explode in a glass tube one-seventh of an inch in diameter: and this gas was more inflammable than the firedamp, as it consisted of carburetted hydrogen gas mixed with some olefiant gas. In exploding mixtures of fire-damp and air in a jar connected with the atmosphere by an aperture of half an inch, and, connected with a bladder by a stopcock, having an aperture of about one-sixth of an inch,* I found that the flame passed into the atmosphere, but did not communicate through the stopcock, so as to inflame the mixture in the bladder : and on comparing the power of tubes of metal and those of glass, it appeared that the flame passed more readily through glass tubes of the same diameter; and that explosions were stopped by metallic tubes of one-fifth of an inch,+ when they were 14 inch long; and this phænomenon probably depends upon the heat lost during the explosion in contact with so great a cooling surface, which brings the temperature of the first portions exploded below that required for the firing of the other portions. Metal is a better conductor of heat than glass: and it has been already shown that the fire-damp requires a very strong heat for its inflammation. Mixture of the gas with air I found, likewise, would not explode in metallic canals * Since these experiments were made, Dr. Wollaston has informed me, that he and Mr. Tennant had observed some time ago, that mixtures of the gas from the distillation of coal and would not explode in very small tubes. +I do not give this result as perfectly exact, as the bore of the metallic tube had not the same polish as that of the tube of glass. 1816.] Sir H. Davy on preventing Explosions in Coal Mines. or troughs, when their diameter was less than one seventh of an inch, and their depth considerable in proportion to their diameter; nor could explosions be made to pass through such canals. Explosions, likewise, I found would not pass through very fine wire sieves or wire gauze. I mixed azote and carbonic acid in different quantities with explosive mixtures of fire damp, and I found that even in very small proportions they diminished the velocity of the inflammation. zote, when mixe in the pr portion of 1 to 6 of an ex. plosive mixture, containing 12 of air and 1 of fire-damp, deprived it of its power of explosion; when 1 part of azote was mixed with 7 of an explosive mixture, only a feeble blue flame slowly passed through the mixture. One part of carbonic acid to 7 of an explo. sive mixture deprived it of the power of exploding; so that its effects are more remarkab: than those of azote; probably, in consequence of its greater capacity for heat, and probably, likewise, of a higher conducting power connected with its greater density. The consideration of these various facts led me to adopt a form of a lamp, in which the flame by being supplied with only a limited quantity of air, should produce such a quantity of azote and carbonic acid as to prevent the explosion of the fire-damp, and which, by the nature of its apertures for giving admittance and exit to the air, should be rendered incapable of communicating any explosion to the external air. If in a close lantern, supplied with a small aperture below and another above, a lighted lamp, having a very small wick, be placed, the natural flame gradually diminishes, till it arrives at a point at which the supply of air is sufficient for the combustion of a certain small quantity of oil; if a lighted taper be introduced into the lantern through a small door in the side, which is instantly closed, both lights will burn for a few seconds, and be extinguished together. A similar phænomenon occurs, if, in a close lantern, supplied with a quantity of air merely sufficient to support a certain flame, a mixture of fire-damp and air is gradually admitted: the first effect of the fire-damp is to produce a larger flame round that of the lamp, and this flame, consuming the oxygen which ought to be supplied to the flame of the larap, and the standard of the power of the air to support flame being lowered by the admixture of fire-amp and by its rarefaction, both the flame of the fire-damp and that of the taper are extinguished together; and as the air contained a certain quantity of azore and carbonic acid before the admission of the fire-damp, their effect, by mixing with it, is such as to prevent an explosion in any part of the lantern. I tried several experiments on the burnNEW MONTHLY MAG.-No, 25, 41 ing of a flame in atmospheres containing fire-damp. I inclosed a taper in a little close lantern, having a small aperture brow, and a larger one above, of such size that the taper burned with a flame a little below its natural size. I placed this lantern, the taper being lighted, on a stand under a large glass receiver standing in water having a curved tube containing a little water adapted to its top to confine the air, and which was of such a capacity as to enable the candle to burn for some minutes; I then rapidly threw a quantity of fire-damp into the receiver, from a bladder, so as to make the atmosphere in it explosive. As the fire-damp mixed with the air, the flame of the taper gradually enlarged, till it half filled the lantern; it then rapidly diminished, and was suddenly extinguished without the slightest explosion. I examined the air of the receiver, after the experiment, and found it highly explosive. I tried similar experiments, throwing in mixtures of air and fire-damp, some containing the maximum and others the minimum of fire-damp necessary for explosion and always with the same satisfactory results. The flame considerably increased, and was soon extinguished. I introduced a lighted lantern to which air was supplied by two glass tubes onetenth of an inch in diameter, and half an inch long, into a large jar containing an explosive mixture of 1 part of fire-damp and 10 parts of air; the taper burned at first with a feeble light, the flame soon became enlarged, and was then extinguished. I repeated these experiments several times, and with a perfect constancy of result, It is evident, then, that to prevent explosion in coal-mines, it is only necessary to use air-tight lanterns, supplied with air from tubes or canals of small diameter, or from apertures covered with wire gauze placed below the flame, through which explosions cannot be communicated, and having a chimney at the upper part, on a similar system for carrying off the foul air; and common lanterns may be easily adapted to the purpose, by being made air-tight in the door and sides, by being furnished with the chimney and the system of safety apertures below and above. The principle being known, it is easy to adopt and multiply practical applications of it. The first safe-lantern that I had constructed was made of tin-plate, and the light emitted through four glass plates in the sides. The air was admitted round the bottom of the flame from a number of metallic tubes of one-eighth of an inch in diameter, and an inch and a half long. The chimney was composed of two open cones, having a common base perforated with many small apertures, and fastened to the top of the lantern, which was made tight in a pneumatic rim containing a little oil; the upper and VOL. V. G 42 Sir H. Davy on preventing Explosions in Coal Mines. [Feb. 1, lower apertures in the chimney were about one-eighth of an inch: the lamp, which was fed with oil, gave a steady flame of about an inch high, and half an inch in diameter. When the lantern was slowly moved, the lamp continued to burn, but more feebly; and when it was more rapidly moved, it went out. To obviate this circumstance, I surrounded the bottom of the lantern with a perforated rim; and this arrangement perfectly answered the end proposed. I had another chimney fitted to this lantern, furnished with a number of safety tinplates of the sixth of an inch in diameter, and two inches long: but they diminished considerably the size of the flame, and rendered it more liable to go out by motion; and the following experiments appear to show, that if the diameter of the upper orifice of the chimney be not very large, it is scarcely possible that any explosion produced by the flame can reach it. I threw into the safe lantern with the common chimney, a mixture of 15 parts of air and 1 of fire-damp: the flame was immediately greatly enlarged, and the flame of the wick seemed to be lost in the larger flame of the fire-damp. I placed a lighted taper above the orifice of the chimney: it was immediately extinguished, but without the slightest previous increase of its flame, and even the wick instantly lost its fire by being plunged into the chimney. I introduced a lighted taper into a close vessel containing 15 parts of air and 1 of gas from the distillation of coal, suffered it to burn out in the vessel, and then analysed the gas. After the carbonic acid was separated, it appeared by the test of nitrous gas to contain nearly one-third of its original quantity of oxygen; but detonation with a mixture of equal parts of hydrogen and oxygen proved that it contained no sensible quantity of carburetted hydrogen gas. It is evident, then, that when in the safelantern the air gradually becomes contaminated with fire-damp, this fire-damp will be consumed in the body of the lantern; and that the air passing through the chimney cannot contain any inflammable mixture. I made a direct experiment on this point. I gradually threw an explosive mixture of fire-damp and air into the safe lantern from a bladder furnished with a tube which opened by a large aperture above the flame; the flame became enlarged, and by a rapid jet of gas I produced an explosion in the body of the lantern; there was not even a current of air through the safety tubes at the moment, and the flame did not appear to reach above the lower aperture of the chimney; and the explosion merely threw out from it a gust of foul air. The second safety-lantern that I have had made is upon the same principle as the first, except that instead of tubes, safely-canals are used, which consist of close concentric hollow metallic cylinders of different diameters, and placed together so as to form cicular canals of the diameter of from onetwenty-fifth to one-fortieth of an inch, and an inch and seven-tenths long, by which air is admitted in. much larger quantities than by the small tubes. In this arrangement there is so free a circulation of air, that the chimney likewise may be furnished with safety-canals. I have had lamps made for this kind of lantern which stand on the outside, and which may be supplied with oil and cotton without any necessity of opening the lantern; and in this case the chimney is soldered to the top, and the lamp is screwed into the bottom, and the wick rises above the air canals. I have likewise had glass lamps with a single wick, and Argand lamps made on the same principle, the chimney being of glass, covered with a metallic top containing the safety-canals, and the air entering close to the flame through the circular canals. The third kind of safe lamp or lantern, and which is by far the most simple, is a close lamp or lantern, into which the air is admitted, and from which it passes, through apertures covered with brass wire gauze of one-two-hundredth of an inch in thickness, the apertures of which should not be more than one-two-hundredth of an inch; this stops explosions as well as long tubes or canals, and yet admits of a free draught of air. Having succeeded in the construction of safe-lanterns and lamps, equally portable with common lanterns and lamps, which afforded sufficient light, and which bore motion perfectly well, I submitted them individually to practical tests, by throwing into them explosive atmospheres of fire-damp and air. By the natural action of the flame drawing air through the air canals from the explosive atmosphere, the light was uniformly extinguished; and when an explosive mixture was forcibly pressed into the body of the lamp, the explosion was always stopped by the safety apertures, which may be said figuratively to act as a sort of chemical fire-sieves, in separating flame from air. But I was not contented with these trials. aud I submitted the safety canals, tubes, and wire-gauze fire-sieves, to much more severe tests: 1 made them the medium of communication between a large glass vessel filled with the strongest explosive mixture of carburetted hydrogen and air, and a bladder two-thirds or one-half full of the same mixture, both insulated from the atmosphere. By means of wires passing near the stop-cock of the glass vessel, I fired the explosive mix ture in it by the discharge of a Leyden jar. The bladder always expanded at the moment the explosion was made; a contraction as rapidly took place; and a lambent flame played round the mouths of the safety |