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242 THE PHOTOGRAPHIC NEWS, [MAY 22, 1868. Silver is abstracted from it by every plate immersed, and nitrates of the base employed in the collodion and iodide of silver, as well as ether and alcohol, constantly accumulate and furnish the elements of other and complex changes. These and other elements of uncertainty exist with the purest materials and the most perfect conditions, and are inherent in the process. The wonder is, not that uncertain ties exist, but that, with so many elements of change not under strict control, so much good work is done with so much precision and regularity by so many photographers. Further, we must contend that if much greater difficulty and uncertainty existed than really does prevail, the reme dies proposed by Mr. McLachlan can in no way tend to greater certainty. The basis of his proposal is the use of an impure sample of nitrate of silver, of unknown impurity, difficult to procure, and still more difficult to identify. Need the conditions of uncertainty be carried further ? We need not dwell on the uncertainty involved in adding one empirical remedy to various collodions of unknown and vary ing constitution, nor to the uncertainty involved in using by preference sulphate of iron of unknown impurity. We have on a former occasion remarked, we maybe re minded, that assuming the facts stated to be true, they were important and interesting. This is undoubedly true ; but they do not furnish remedies for any of the inherent uncertainties of the collodion process. If it be true that a solution of nitrate of silver undergoes a change, under the prolonged action of sunlight, other than that already recog nized, and that, in consequence, it acquires a property, not only of holding a large portion of oxide of silver in solution, but of preventing it being readily reduced, the fact is both interesting and important, inasmuch as, if true, it must lead to more rapid, and, possibly, more perfect results; but it affords no immunity from the constant changes going on in collodion, the constant accumulations and change of condition in the nitrate bath, the constant possi bility of the action of impurities beyond the control of the photographer, and the varying other elements of change and uncertainty which are the chief sources of the troubles which occasionally beset the photographer. If the fact stated by Mr. McLachlan, that a bath treated as he describes suddenly and of its own impulse eliminates from itself excess of iodide of silver, it is very important and interesting, as getting rid, not of an uncertainty, but of a certain source of occasional defect, with less trouble than is involved in the method of diluting and filtering. But without denying Mr. McLachlan’s facts, which can only be verified or disproved after many months of careful experiment, we may point out that there are certain con siderations in regard to them which require weighing. In the first place, the best evidence he could have furnished to a meeting (experiment being impossible) would have been a sight of some negatives of exceptional excellence. We know that Mr. McLachlan is a capable practical photographer, and produces fine negatives, as do most photographers of position; but the gentlemen present at the Photographic Society would not have been slow to recognize any excep tional qualities. Further, there is already a difference of evidence on the facts. Mr. Spiller states that a bath prepared according to Mr. McLachlan’s instructions, and sunned for seven weeks, was made alkaline and unfit for work by the addition of 6 drops of a 1-grain solution of caustic potash, the propor tion of the alkali to the silver salt being as 1 to 56,000. Mr. McLachlan states, that instead of 6 drops, " quite a gulf” of the potash solution was added. A mistake exists some where, and we leave our readers to select between the preci sion of a gentleman of long experience as a practical chemist, accustomed to attach value to infinitesimal proportions, and that of Mr. McLachlan, who is certainly an impulsive and enthusiastic gentleman, although, as he says himself, no chemist. And here we have a word of grave remonstrance for Mr. McLachlan, which he must take in good part, as it is written in a friendly spirit. He prefaced his last communication by stating distinctly that he was no chemist, and he then pro ceeded, not simply to state the facts of his experience and observation, but to indulge in a series of theoretical specula tions of the most incongruous character, and to speak of chemical reactions of the most impossible character. Wo forbear giving examples; but we suggest that we are prepared to listen attentively to the observations and experiences of Mr. McLachlan as those of a gentleman who has worked hard and enthusiastically in experimental photography, and whose work, guided by more chemical knowledge, would have been more valuable; but we must ask him to avoid encumbering his facts with chemical ter minology misunderstood and theory misapplied, as these things materially impair the practical value of his infor mation. Having pointed out—with the candour for which he asks —the misconceptions which we think Mr. MeLachlan has laboured under as to the existing knowledge of photography, and his somewhat erroneous estimate of the scope and bear ing of the facts he has stated, we shall in our next have a few words on the real importance and value of his communica tion, which, notwithstanding the errors we have pointed out, contains much suggestion for which photographers will be SWAN'S CARBON PROCESS. Notwithstanding the large number of excellent carbon prints which have been issued by Mr. Swan from his estab lishment at Newcastle-on-Tyne, and the fine examples which have been exhibited by Mr. Mayall, Mr. Cherrill, and others, we learn from personal and written communications with photographers that a doubt exists in some quarters as to whether these things are indications of anything more than exceptional success, and whether, after all, the carbon pro cess can be generally worked with success as a commercial enterprize. It will interest photographers generally, and especially those who have doubted the practical character of the carbon process, to hear of the progress of this mode of printing at the establishment of M. Braun, ot Dornach. It is not much more than two years, if we remember aright, since Mr. Swan’s process was inaugurated at Dornach. During that time it has been gradually developed, and has displaced silver printing. The number of persons now regularly engaged in the establishment in the production of carbon prints is eighty ; and the demand for the pictures is so great that, with this large staff, M. Braun finds it impossible to accumulate stock, the demand being in advance of the pro duction. One fact like this is worth a hundred arguments on the practical and commercial character of carbon printing. We hope ere long to see this mode of printing as exten sively in use in this country. The “ Autotype Company," to which we have before referred as having acquired the patent of Swan’s process in this country, is steadily pro gressing with arrangements' for an exceedingly perfect and extensive system of art reproduction by means of carbon printing, which promises more for the popularization of really good art, and giving the examples a permanent form, than has ever yet been attempted in this country. Ths results now exhibiting at the company’s gallery in the Haymarket leave no room for doubt as to its success. PICTORIAL EFFECT IN PHOTOGRAPHY; Being Lessons in Composition and CIAROscURA for PHOTOGRAPIIERS. BY H. P. ROBINSON. Chapter XVII. " Every man is always present to himself, and has, therefore, little need of his own resemblance, nor can desire it but for the sake of those whom ho loves, and by whom he hopes to be remembered: this use ot the art is a natural and reasonable consequence of affection, and though, like other
