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Bt ome. MR. ALEXANDER COWAN’S LABORATORY IN PORCHESTER TERRACE. Mr. Cowan’s name has not been before the world in connec tion with a grand discovery, but he has a much higher claim upon the sympathies of his brother photographers than could be conferred by any such distinction. His sagacity as an experimentalist, his ingenuity as a mechani cian, his deftness and cunning in manipulation, his ready wit in designing and inventing, and above all his delicate and skilful touch, combined with a deep and thorough knowledge of the art-science he loves so well, have placed him in the forefront of photographic authorities of the practical school. And as there never was one more ready to make public the fruits of his labours, just as there certainly is none whose results are better worth making known, we have in Mr. Cowan one to whom all photographers are very much indebted. We need not point out what Mr. Cowan has done in the past. Among the “ Standard Formula ” in the YEAR-BooK, Mr. Cowan’s name will be found in connection with one of the most practical forms of development yet devised ; while to every branch of photographic manipulation pretty well, Mr. Cowan has contributed some improvement or modification of value. Mr. Cowan’s laboratory in Porchester Terrace is precisely what one would expect from its occupant. If it is not very Spacious, it is at any rate commodious, and we doubt much whether any other chemist or photographer could be found who possesses half the number of useful arrangements and clever contrivances within a space so limited. But we must stay our encomiums if we are to describe anything of the contents of the busy little spot; only, before we begin, we make an apology to Mr. Gowan himself for the very imperfect manner in which we fear his manifold attractions will be put before the reader. Mr. Cowan’s dark-room differs, we may remark in the first place, from other dark-rooms, in the fact that it is not dark ; or, rather, we should say, it is always perfectly light, except, and except only, for the few seconds that a plate is under the developer. This is due to the simple circumstance that the gas-tap—something like an organ stop, to push in or out—is so convenient to hand. The supply of gas is arranged so that this stop never extin guishes, but only lowers the light. To say that everything is neat, precise, and in apple-pie order throughout, and arranged after a perfect system, is to say little. The labor atory resembles a beehive as much for its symmetry' as for its compactness. Here on a shelf is a row of six bottles, numbered from 1, 2, 3, 4, 6, 8, the solutions made up according to “ Cowan’s method of varying the proportions of bromide in the developer,” as shown in the Standard Formulss of the Year-Book. Under the shelf is another smaller one, that admits “ standing-room only ” for one bottle; when a bottle is in use, instead of putting it back into the row, it is placed by itself below, and in this way the manipulator is always sure which particular solution he has been using. The plan is a most practical one for the photographic laboratory, where one has to deal with many bottles in an uncertain light. Here is a cheap furnace or copper that may be constructed with an outlay of half-a-crown, Mr. Cowan tells us, and which he employ principally for mixing together several batches of emulsion. He takes from under one of the benches an old hyposulphite cask, and puts it into the middle of the laboratory. Its sides are roughly pierced with holes to admit air, and through one of the lowest of them is thrust a rubber gas-tube. A Bunsen burner, which most photographers possess—there are few photographers who do not possess the old hypo cask and few feet of gas tubing as well—is now placed on the bottom of the cask and connected with the tubing, and the apparatus stands ready for lighting. I he " copper ” to contain the water, or anything else to be heated, is simply a big vessel of galvanised iron, to be pur chased anywhere for half-a-crown, and this, when the lamp is lit, is lifted upon the cask. A firm, portable, and cheap heating arrangement is thus at hand. For mixing batches of emulsion, Mr. Cowan takes an earthenware jar (Doulton’s chemical jars are best and cheapest), with “ shut-over ” top of three or four gallons capacity, and this, containing the emulsion, is put in the “copper” of warm water. We give sketch ef the arrangement; a is the j ar, which goes into &, the galvanised iron “ copper,” while c is the cask that receives b. Mr. Cowan, of course, makes his own emulsion, and so successfully, that the plates are practically all of the same standard of sensitiveness. He controls matters in two ways— by manufacture and development. Thus, in his preparation of batches of emulsion, he employs always solutions of the same strength. There is no preliminary weighing or fuss over calculations of weights, as a commencement to work. This is all obviated by keeping huge stock bottles of solutions of given strength of silver, bromine salts, &c., so you may get to work at once. The proportions of liquid taken are rigidly adhered to. Mr. Cowan has a series of glass flasks at hand, each marked with its capacity, and these have only to be filled, to measure off the required quantities. Then, after several batches of emulsion have been prepared—Mr. Cowan is just now using the boiling method, and makes about forty ounces at a time—these are all mixed together in the manner we have described. Such a plan of proceeding cannot fail to give a very uniform, material; but to work always to the same standard, Mr. Cowan makes with his composite batch two or three practical essays. He exposes a dozen plates, and develops them experimentally with his row of solutions, containing various proportions of bromide. When he gets a negative that suits him, he looks at the No. of the bottle employed, notes it, and then gives instructions that that bottle, and no other, is to be employed for the next few months, or until the new batch of plates is exhausted. Before passing to another subject, we may mention that Mr. Cowan still gives preference to a developer containing citric acid. Of Mr. Cowan’s plate-holder we give a sketch once more, since it is, in our opinion, the handiest device yet made