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The photographic news
- Bandzählung
- 12.1868
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- 1868
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- Hochschule für Grafik und Buchkunst Leipzig
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- Bandzählung
- No. 505, May 8, 1868
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The photographic news
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Band 12.1868
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- Titelblatt Titelblatt I
- Kapitel Preface III
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- Register The Index To Volume XII 619
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226 THE PHOTOGRAPHIC NEWS; [May 8, 1868. some of M. Marion’s new transparent pellicle, and described its uses. M. DESPAQUIS described the process employed by himself for the preparation of carbon prints on collodion-cuir, and gave a practical demonstration of his method of developing and mounting the prints. The Society thanked M. Despaquis for his communication, and requested him to prepare a description of the process for publication in the Bulletin. The proceedings then terminated. Oldham Photographic Society. The Ordinary Meeting of the above Society was held on Thurs day, the 30th inst., the President, Mr. John Green, in the chair. After the minutes of the previous meeting had been read, Messrs. John Dalton and Wm. Fernley were elected members. Mr. Beverley, then read a short paper on the Dry Plate Process, which will appear in our next. There being no other business, the meeting was brought to a close. (otresponence. SEL CLEMENT. Dear Sir,—I presume you have taken the course of inserting the letter from “The Maker of the Sei Clement ” merely as an act of courtesy to a foreign correspondent, who, although pro fessing to be a chemical manufacturer, does not write like a chemist. The writer says, “For me, substances containing carbon are not the only ones that are organic ; but I consider as such all those which contain either hydrogen or nitrogen.” Impossible! Has hydrochloric or nitric acid ever been included in the list of organic bodies? I challenge the writer to quote any authori tative statement to this etfect. On the contrary, the existence of carbon is a sine qud non ; without it no organic compound can be built up. Dr. A. W. Hofmann’s apt definition of organic chemistry declares it to be “ the branch of science which treats of the migration of carbon.” Again, it is suggested that “ the nitrous fumes formed during the combustion have reduced the nascent carbonic acid into car bonic oxide, they themselves being converted into nitric acid.” This view is quite opposed to well-ascertained facts: simply because nitric acid vapour, when heated in a combustion tube, splits up into red nitrous acid and free oxygen; and, in the presence of this latter, it is impossible for a reducing action to be exerted upon the carbonic acid. Your Paris correspondent takes exception to the form of apparatus used in my experi ment, and asserts that it “ was not properly arranged to show any trace of carbon whereas I took especial pains to prove the fact that it did furnish evidence of carbon when I purposely introduced a trace of sugar, after the Sei Clement alone had failed to show any indication of the existence of an organic component by the production of a white precipitate in the lime water. The occurrence of nitrate of magnesia and of a large amount of water, as essential ingredients of the “ Sei Clement, or Pre servative Nitrate of Silver,” is virtually conceded.—I am, dear sir, yours, &c., The Analyst. Mag 1st, 1868. THE PANORAMIC STEREOSCOPE. Dear Sib,—While thanking you for the kind notice in your Journal of the panoramic stereoscope, we shall feel much obliged if you will permit us to correct an error as to the assumption on which the new form is based. This you state to be that “ the angle of natural vision horizontally is only one half of the vertical angle.” We did not intend to convey that impression. What we really meant was, that while the size of two pictures which can be united stereoscopically is limited in the hori zontal direction by the fact that their centres must be as nearly as possible opposite the pupils of the eyes, in the ver tical direction it is limited only by the angle of natural vision, which practically admits of the use of a picture nearly double the height of the width between the eyes. Our aim has been to modify the mode of taking and the instrument for viewing stereographs so as to take advantage of this fact.—We remain, yours, &c., W. Harding WARNER. London, May 5th, 1868. Robert Murray. [We have pleasure in giving insertion to the above expla nation ; but we must point out to our correspondents that the sentence to which they take exception is not ours, but theirs, or that of Mr. Warner, as in making an allusion to such a claim we felt it right to do it in the words of the claimant. The descrip tion of the instrument now before us, in Mr. Warner’s hand writing, runs thus:—“ The inventors have discovered and taken advantage of a new and important feature in optics hitherto overlooked by all makers of stereoscopes, viz., that the angle of vision horizontally is only one half of that vertically." Whilst fully recognizing the practical value of the new instru ment for many purposes, and the satisfactory results it gave, we felt it a duty to take exception to what appeared an erro neous statement of principle as the basis of an excellent invention.—Ed.] MODIFIED HONEY PROCESS. Sir,—Thanking your correspondent, Mr. G. Robert Fitt, for his description of a “ Modified Honey Process,” published in the News of 24th April, 1868, I should feel very much obliged if he would give the quantities of honey and water respectively to form the syrup, also the proportion of pure animal charcoal required, and whether the plates will keep some hours after exposure before development without injury, and if they should be flooded with water, or what, before development.—I am, sir, truly yours, M. N. L. 57a, Wimpole Street, May 5th, 1868. PHOTO-LITHOGRAPHY. Sir,—We feel very reluctant to encroach upon the space of a journal devoted to science only, with reference to personal affairs, but we cannot permit statements to be made which, if circulated, may find believers among those who are perfectly uninitiated in photo-lithography. In your number of April 24th, 186 3, you made some remarks as regards the working of a “ new process of photographing on stone ; ’’ and although you find the results excellent, and the application of photography most legitimate, yet you consider these results not to be examples of photo-lithography “ as popu larly understood." You further speak of the results “on good authority,” that the prints are the productions of a “ silver process on a finely- grained stone, and the image is then worked with lithographic chalk,” &c. But the “ good authority ” goes even beyond this in his observations, by stating before the Photographic Society that, “ if he is not mistaken, the prints he has seen lately from a new process of photographing on stone ” have been produced in the way described by you under the head “ Griggs’ Litho graphic Process,” and in which he states he obtained by the same means that he employed some four years ago ; viz., by coating a grained stone with silver. We do not know of any other house in England or on the Continent engaged at present in working commercially “ por traits by photo-lithography,” therefore we are compelled to come forward as the owners of the “ new process of photographing on stone,” for the purpose of answering and contradicting those statements. An apprentice in lithography will be in a position to explain as to what the effects of lithographic chalk may be when being put upon a silver surface, or, indeed, any other surface but the cleanest surface of the stone itself. We are fully alive as to the motives which prompted those statements, and therefore will confine ourselves simply to the declaration that our productions are the results of photo graphing direct on the stone with materials capable of yielding proofs in printers’ ink only. We are not quite blind to the hints of your “ authority ” that he does not keep back useful informa tion “ selfishly,” nor do we mind his allusions that ho does not pride himself on “ secret dodges,” nor do we care for his pointed invitation to come forward and “ give up freely the results 05 our labours.” Nothing will induce us, beyond tins letter, to ba drawn into a controversy, for many and “ obvious reasons. | Suffice it to say that the means for obtaining lithographo by a
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