The Optical Magic Lantern Journal (October 1890)

34 The Optical Magio Lantern Journal and Photographic Enlarger. a few coppers per pound. A company has been formed for supplying various articles, including optical instruments, made of this metal. * s s Tue exhibition of the Photographic Society of Great Britain, 3a, Pall Mall, S.W., opened on September 27, and will continue until Nov. 12. Photographic lantern slides will be shown with the society’s lantern. As we go to press on the eve of the opening, we shall have to postpone our remarks until next issue. R 2 2 Proressor B. J. Matpen has lately had a magnificent triple lantern built by Mr. W. C. Hughes, of Kingsland. This is replete with numerous fittings and novelties, which will enable Mr. Malden to give with certainty those fine effects and registrations for which he is so well known. * s » THe first meeting of the season of the Lantern Society will take place on the 13th inst., at 20, Hanover-square, when Mr. Andrew Pringle will give a lecture on “Modern applications and appliances of the lantern,” * ¢ e We have received a visit from a London gentlemian, who assures us that he will soon be able to show us a photograph on the screen with stereoscopic relief. The slide that is to be put inthe lantern ts, he says, ‘‘a single picture with every thing standing out.’’ Should we see or receive such a picture, due notice will be given. * ol La Tuz photographic business of Mr. F. Crowley, of Leamington, has lately, through the instrumentality of the well-known photo business agent, Mr. H. J. Beasley, of 65, Chancery-lane, been sold to Mr. H. E. Sawyer. ; * * . THE total proceeds of the award from the Drapers’ Hall Exhibition to the Photographers’ Benevolent Association has amounted to £4 2s. 5d. s a > Dr. Kassver, of Breslau, has discovered a new method of obtaining oxygen from the air. Water is poured upon a mixture of peroxide of barium and ferricyanide of potash, and oxygen is given off. The oxygen thus obtained is said to be of great purity ; * s s A CORRESPONDENT suggests the employment of’ paver, pressed and chemically prepared, for making lantern bodies, lens tubes, and slide frames, as it would tend considerably towards lightness. Paper can be prepared very hard and firm, and is a non-conductor of heat. Dry Collodion Plates for Lantern Transparencies. Wuite the wet collodion process is that by which the manufacturer on a large scale can make most progress in his output of lantern slides, yet to the amateur who wishes to make only a dozen or two when it suits his whim or convenience it certainly entails a little trouble and mess, for the nitrate of silver bath must be kept in gcod condition, which may possibly not be the case when he decides upon using it. Dry collodicn, by which we mean dry collodion plates, proves much the more convenient process of the two, for the plates can be made so as to keep well for several weeks at least, and besides they posscss this great advantage, that while they can be printcd in the camera, they can also be printed in contact with the negative, which cannot be done with wet collodion. Although dry plates can be prepared by the agency of the nitrate bath, the emulsion process is so much more handy, and the pictures are so good that we will here confine ourselves to the latter. Its convenience is very great, for witha bottle of emulsion at hand, the coating of a few plates can be proceeded with, without any special preparation beyond lighting the yellow—not the red lamp in this case—and dusting the required number of previously cleaned plates. In all cases when lantern slide collodion cmulsion can be purchased, we recommend this to be done; but there is no doubt that a great nuinber of those who employ collodio-bromide make it for themselves, for this operation is not attended by any difficulty. The proportions in the following are those published by Mr. F. C. Beach, but previously used by others. Prepare a stock supply of plain collodion, by placing 2202. of methylated alcohol in a large bottle, then adding 1oz. of gun cotton, prepared at a high temperature ; and after giving it a shake, adding 180z. of sulphuric ether, by which the cotton will be dissolved. To roz. of this plain collodion add 13 grains of bromide of ammonium dissolved by aid of heat in 13 drachms of methylated spirits and 20 minims of distilled water, and after well shaking take to the dark room and add 20 grains nitrate of silver dissolved in 12 minims distilled water. Keep in the dark room for twenty-four hours, shaking up at intervals. Next pour the emulsion into a large flat dishand allow the solvents to evaporate, breaking up the thick skin occasionally with an ivory paper-knife. Now wash with distilled water until all the soluble salts are removed. Dry the pellicle by squeezing in calico and then submitting to a moderate heat. All this must be