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THE PHOTOGRAPHIC NEWS. d jalap animal e-tenth harma- that is, damp, to mili- e testi- , to the t it will rth six is loses r seven its use j ounce ess was articles rolume, on the in the nerally id; the uckle's n of a i three copper g about . The phurio n-inch. ipound graphs tred in sbomo easily atensi- sity by : wash- loride is the 11 ways ent to j sufli- n. entity, respec- iot the lr. Fox lotype etable : from at the erent, cfectly 5, that i, and ierally welve s have irticle en wo would r toa a was until rbing dated IANAO lan to • each > pub- ative ice of great Ex- en to over ts:— y of e In- Mar- k as a i for Vol. VI. No. 218.—November 7, 1862. I half tone in photolithographs. great desideratum in photolithography has hitherto been, Eone, or gradation of tint, without lines or points, Wing or stippling. This has not been satisfactorily pro- C* By any of the known processes. Col. Sir Henry 168Jias just announced it as an accomplished fact. The I "oving letter appeared in the Times of Tuesday last.— “ PHOTOZINCOGRAPHY. A®,—I shall be glad to be allowed to announce, through 66olumns of the T’imes, that we have accidently made the Bortant discovery that the paper prepared with bichromate POtash and gum only, as described in the work on Photo- OWphy lately published by Messrs. Longman and Co., 31 only kept for a week or ten days in the dark, yield half 62 and consequently give us lithographic or zincographic 38 from any photograph. wa enclose two copies of a print produced in this manner, although not so perfect as we can undoubtedly make A Will prove that the object so long sought after has now “attained.—I am, Sir, your obedient servant, “ Henry James, Colonel Royal Engineers. ^nance Survey Office, Southampton, November 3. r, Pouncey in a letter, an extract from which we give in f Bber column,* announces similar progress, and challenges 0Tination at the meeting of the Photographic Society. G"esday night he was present at the meeting, and pro- l several specimens, some of which were photographs, others impressions in printers’ ink, produced direct from legative. They were not received very favourably by a Meeting, a spirit of distrust on the one hand, and of (8onism on the other, seemed to prevail, and a general s,5nt from Mr. Pouncey ‘s assumption, that they were equal J 1 Yer prints, was expressed. viProtr own part, we feel some difficulty in expressing an 1"lon on the subject. We have every disposition to do BEouncey full justice, and wo feel the difficulty of doing w hout having silver prints from the same negatives, which to compare his specimens. They were certainly 1800d pictures, and appeared to be from somewhat bard qives; but they certainly possessed some gradation, (.proposition to take any negative submitted to him, and M"ce from it a photolithograph, or an image in any U^r’s ink, which might be brought for the purpose, as L ect in half tone as any silver print from the same nega- • Certainly appears a fair one, and should, we think, be v On the other hand, we would suggest to Mr. Pouncey, t We do it with every wish to avoid offence, since he holds v c onviction that he has been ill-used by photographic vSties and the photographic press, that, however uninten- wAlly, he seemed to approach the meeting in a spirit of Conism, and that begets antagonism. That, moreover, , Sontravened the custom of the society in wishing it 44ea with a secret, or, at least, an unrevealed process. 1^ that, further, he had, on former occasions—with % 2e8t of motives it might be—issued prints as the ’M of one process, which were produced by another; 5i.,Ihis circumstance might explain some distrust. We Ey&, however, from what we saw of his results, on k slay, night, that they are worthy of further attention, , ha he glad to see more of them. And, personally, we sadd that we shall have pleasure in allowing him to San article in type, 011 “ Photozincography, Photolithography, and Photo- Nvee and their Inventors," is compelled to stand over until the select a portrait negative, from which to produce a photo lithograph for comparison with a silver print. In an interview with Mr. Maxwell Lyte, just before his return to France, he entrusted us with a verbal description of a method, by which he suggests that half tone might be produced in photolithographs. It was his wish that we should have described it to the meeting on Tuesday night; but the protracted character of the meeting, and a severe hoarseness under which we were labouring, induced us to publish it in this form. Mr. Lyte proposes to obtain half tone in photolithographs, by taking advantage of the method adopted by M. Fargier, for obtaining half tone in carbon prints. M. Fargier, be lieving that the difficulty in obtaining half tone in carbon prints arose from the fact, that the action of light upon a film of gelatine, bichromate of potash, and carbon, failed to penetrate in the half tones much further than the surface, and that thus, when the sheet of paper on which it was spread was immersed in water, the unaltered gelatine underneath the half tones being readily washed away, carries off at the same time, the slightly altered portions which really constitute the half tones. The deep shadows being more perfectly acted upon by light, are, of course, less soluble, and remain. The result is a black and white picture, without proper grada tion. The same fact will obtain in photolithography from the same causes. M. Fargier overcomes the difficulty, by applying the film of gelatine, carbon, and bichromate of potash to glass, and after exposure, coating the surface with collodion. The film is then removed from the glass, and the unaltered gelatine, &c., dissolved. By this mode of manipulating, the delicate half tones are preserved, and remain attached to the collo dion, instead of being, as in the other method, washed away. Mr. Lyte proposes to apply this method to photolitho graphy, with this difference to suit the case: instead of carbon in combination with gelatine and bichromate of potash, he proposes to use powdered bitumen, and after treating the plate after M. Fargier’s method, he would transfer the image so obtained, to a lithographic stone, by the aid of heat. The half tone which is produced by this treatment, in a carbon print, would, he conceives, be thus secured on the lithographic stone. So far as the production of a properly graduated image on the stone is concerned, this method appears very promising. How far prints with half tone would be obtained, remains to be tried. The experiment is certainly well worthy of attention. - • ON THE PERCEPTION OF RELIEF. BY PROFESSOR EDWIN EMERSON, OF TROY UNIVERSITY. [We have been favoured by the courtesy of Professor Emerson, and the prompt and courteous attention of Professor Silliman to his request, for early proofs of the following interesting contribution, which appears in Silliman’s American Journal for November. We especially commend attention to it as a lucid explanation, of the not generally understood difference between two distinct phenomena, relief and perspective.—Ed. Photo. News.] “ Professor Cima of Turin, has sent us the description (says the editor of the Cosmos) of a stereoscopic experiment which is not without interest. He takes the picture of a front view of a human head, executed either in crayon or lithograph or copper plate, and which is three or four centimetres in height ; this he cuts into two parts along a line which coincides with the vertical axis of the nose; he takes one of these halves in each