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478 THE PHOTOGRAPHIC NEWS. LJULY 27, 1883. and terror of the miner, as fire-damp. The formula of methane is CH, It is a colourless gas, becoming liquid only under ex treme cold and pressure. Its sp. gr. is '55. Here is a cylinder of it: observe the bright, smokeless flame, characteristic of the paraffins generally. In this short, stout tube, there are confined four volumes of oxygen, with two of methane ; applying alight, the brisk detonation suggests that methane, at least, has kindred feelings to oxygen. But the methane exists no longer; at the moment of union, water and carbon dioxide—the dreaded choke damp—were formed— CH+0,=C0,+2H,0 Marsh gas is the invariable concomitant of slow organic decom position. The formation of coal was attended with evolution of this gas, large volumes of which are often stored in coal mines. The mud-volcano of Bulganak, in the Crimea, belches forth pure CH, The fire worshippers of Baku, according to O’Donovan,* prostrate themselves before a stream of this gas. It is also seen dancing over marshes, ablaze, as Will-o'-the-Wisp. Methane, and the three following members, ethane (C,Hg), propane (C,Hg), and butane (C,He), are gases of density, increasing with their molecular weights. The fifth, pentane (C,H,2), is a liquid at 38°C., and so till the sixteenth, hexdecane (C,H,3), solid at 21°C. Ethane (C,Hg) is noteworthy as the parent of alcohol, ether, and acetic acid. (To he continued.) Gorzespombence. STANDARD LIGHT. Dear Sir,—As the question of a standard light is now in order, I call to mind a recollection of a lamp that was devised for giving a standard light, and it appears to me about what is wanted. remedy. If we must have pound tins, I would suggest that they contain the amount in half-ounce and quarter ounce packets, which would be infinitely more convenient than having to weigh out, perhaps at the last moment, when time is valuable.—Yours obediently, H. W. B. A TIGRESS IN ITS LAIR. Dear Sir,—I send you by “ book post ” a copy of a photograph I took a short time ago in the Jungles, and should be glad to hear what you think of it. It was taken on a Pall Mall plate. Its chief merit as a picture, however, I consider lies in the pose of the tigress ; and when I tell you that the beast posed herself in the exact position in which her portrait was taken, I think you will agree with me that it was a lucky chance which a photographer does not get every day. To account for her keeping so still, I may mention that she received a ball through the heart before the camera was brought to the front.—Yours faithfully, W. W. Hooper, Major, 4thP. W. 0. L. Cav. Kamplee. [Major Hooper’s picture is, indeed, a realistic one. In a rocky recess, formed of big gray boulders, lies stretched the fallen “Empress of India,” its striped body and finely marked head the embodiment of lissom strength and ferocity. On the stay-at-home mind the effect of the picture is particularly graphic ; a dozen chapters could not convey to the senses the terrible feeling of reality that Major Hooper is able to bring home by his powerful photograph.—Ed. P.N.] Aroceedings of Societies. Fig. 1, Opening for filling lamp; 2, reservoir for fluid ; 3, connection to Wick chamber; 4, wick chamber; 5, opening for wicks. The chamber No. 4 is to be of a certain diameter and deepness. The wicks are of platinum wire taken just so many to fill the chamber, and are to be a trifle longer than the chamber is deep. Fluid Used.—Pure alcohol of a standard strength, with a small but definite quantity of pure spirits of turpentine mixed therein. It is evident that each lamp made strictly after standard, and fed with standard fluid, will give an equal light with a standard metre having as many numbers as may be deemed necessary, and a distance set at which the plate shall be exposed; and for a certain specified length of time to give the No. 10 as a unit. If dry plate makers were to use such a lamp, and give the number indicated by meter on each packet of plates, it would be a standard that could be used the world over, and a great help to the users.—Yours, Jex. Bardwell. Detroit. PACKING PYROGALLOL. Dear Sir,—Will you kindly grant me space to protest against the present mode of packing pyrogallol. In the old days it was not thought too much trouble to cram ounces into separate bottles; but now one never sees such a thing, and in place we get larger sized bottles, or pound tins, which I must say are very inconvenient. Of all operations, there is none more utterly odious than weighing “ pyro ”—especially if one should happen to run short of solution, and have a sitter waiting. Now that I have had my grumble, let me suggest a * O’Donovan, " Merv Oasis,” Photographic Society of Great Britain. The usual monthly Technical meeting of this Society was held on Tuesday evening, July 24th, at 5a, Pall Mall East, Captain Abney, R.E., F.R.S., in the chair. Mr. ADDENBROOKE exhibited a photograph he had taken of the very bright forked lightning which appeared during a thunder storm recently in London. A conversation arose re specting any influence which electricity in stormy weather might have upon gelatine emulsion; but no observation had been made upon this matter. The Chairman then alluded to some transparencies which had been fixed in windows having become tarnished, and desired to know whether damp would affect them. It seemed to be admitted that proximity to the effluvia of gas burnt in rooms would considerably affect that class of picture. Mr. Warnerke also stated that some valuable film negatives were sent to the Paris Exhibition, and the cases having to wait a long time in an exposed shed before being opened, he found that damp had destroyed many of them. Mr. Payne Jennings had also lost some negatives from his late store room having been damp. Both the films and the negatives on glass, gelatine, as well as collodion, had brown markings upon them, and it had been decided that they had no relation to silver deposit or to any action of hypo.; therefore they must have arisen from damp. The Chairman, in alluding to this subject, said that if a drop of water got spilt or splashed on to a geiatine negative, it dis coloured the part. It was suggested that re-wetting the plate would entirely remove the effect, as also that rain drops some times contained nitric acid; but, it was thought, so little as not to be considered. . s Mr. Ackland thought that if water removed the stain, 1 would show that it was due to physical causes. Mr. D. S. Davis then alluded to the fact of halation occurring to some negatives he had taken upon gelatine emidsion plates, and said it raised the question whether any preparation 0 emulsion could be made to induce a large amount of density, or whether resort should be had to backing to correct this tendency to halation; when it appeared to be the general opinion that the better plan was to back the plates. The conversation t en drifted into the various kinds of backing most suitable to us, burnt sienna and gum-water being recommended ; asphan ” being also thought good, excepting that it gave a brillisnt ®u face, and was not so suitable as pigments like sienna, wW g