The photographic news

• Bandzählung: 35.1891
• Erscheinungsdatum: 1891
• Sprache: Englisch
• Signatur: F 135
• Vorlage: Hochschule für Grafik und Buchkunst Leipzig
• Digitalisat: Hochschule für Grafik und Buchkunst Leipzig
• Digitalisat: SLUB Dresden
• Rechtehinweis: Public Domain Mark 1.0
• URN: urn:nbn:de:bsz:14-db-id1780948042-189100009
• PURL: http://digital.slub-dresden.de/id1780948042-18910000
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• Sammlungen: LDP: Historische Bestände der Hochschule für Grafik und Buchkunst Leipzig
• Sammlungen: Fotografie
• Strukturtyp: Band

• Digitalisat: SLUB Dresden
• Strukturtyp: Ausgabe

628 THE PHOTOGRAPHIC NEWS. [September 4, 1891. PHOTOGRAPHIC CHEMISTRY* BY PROFESSOR R. NIELDOLA, F.R.S. Apart from the popularity of photography as an inexpen sive amusement, enabling the amateur to obtain, with comparatively simple appliances, permanent records of places visited, or representations, more or less faithful, of the features of those whose individuality it is wished to bear in remembrance, the subject is becoming of daily increasing importance, on account of the numerous appli cations which photographic processes have found, both in art and in science. For this reason, it is desirable that the claims of photography to be considered a distinct branch of applied science or technology should be urged upon all those who are in any way interested in the advancement of technical education. Some progress has already been made in this direction in certain schools and colleges in this country, but when our efforts are compared with the keen appreciation of the subject which is borne witness to by the splendidly equipped photo-chemical laboratories of the technical high schools of Berlin and Vienna, it will be admitted that in this, as in other depart ments of chemical technology, we have allowed ourselves to sink into a secondary position. It is certainly remark able that the land of Fox Talbot and Herschel—the country which has given to the photographic world all the most important processes discovered since the foundation of the art by Niepce and Daguerret—should nowhere possess a school of photo-chemistry where the subject can be taught from a scientific platform, or where original investigators can find the requisite appliances and the skilled assistance necessary for the prosecution of research. Setting out from the admission that photography must, sooner or later, become incorporated in all schemes of systematic instruction in applied science, I propose, in the present course of lectures, to show how this subject may be dealt with from a chemical point of view. From this it must not be inferred that photography is to be regarded purely as a branch of chemical technology, for it has also its physical side, and the highly trained photographer should be well grounded in the theory and construction of lenses, spectrum analysis, and, in short, in the general principles of optics. Assuming this knowledge to have been acquired, we may proceed to ask how the subject is to be taught, and the consideration of this question is of considerable importance—it is, in fact, of far greater importance than may appear at first sight, for photography is most admirably adapted to bring out into prominence the principles of technical instruction in a subject which is very largely of a chemical nature. The consideration of this question may help to dispel some of the haze with which the much-abused term “technical training" has been surrounded, and it will certainly lead to a clear con ception of the object and scope of these lectures. There are many who identify technical instruction with the teaching of some handicraft, a notion which has, no doubt, arisen from the identification of technical skill * Cantor lectures, delivered at the Society of Arts Theatre. t This is no vain boast. Taking the discoveries in order, we have the silver print and chromatised gelatine emanating from Fox Talbot; the cyanotype due to Sir John Herschel; the collodion process introduced by Scott Archer and Fry ; collodion dry plates by Russell; printing with pigmented gelatine worked out by Swan; gelatino-bromide emulsion introduced by Maddox; and the platinotype process of Willis; to say nothing of the photo-mechanical printing processes, such as Woodburytype, to which English investigators have contributed so largely. with manual dexterity in some mechanical industry. By the adoption, either tacitly or openly, of this narrow definition, the chemical industries have suffered to a very large extent in this country, because their progress is more dependent on a knowledge of scientific principles, and much less dependent on manual dexterity, than any of the other subjects dealt with in schemes of technical instruc tion. Now, in order to give technical instruction in a subject like photography, which is so intimately connected with chemistry, we may adopt one of two courses: The student may become a practical photographer in the first place, and may then be led on to the science of his practice by an appeal to the purely chemical principles brought into operation. This may be called the analytical method. The other method is to give the student a training in general chemistry first, and then to specialise his knowledge in the direction of photography. This may be regarded as a synthetical method. In other departments of technology, and especially in those where the underlying principles are of a mechanical nature, the analytical method may be, and has been, adopted with success. It is possible to lead an intelligent mechanic from his every-day occupations to a knowledge of the higher principles of mechanical science by making use of his experience of phenomena which are constantly coming under his notice. From this it is sometimes argued by those who are in the habit of regarding technical instruction from its purely analytical side, that technical chemistry can be taught by the same method. Some teachers may possibly succeed in this process, but my own experience, both as a technologist and a teacher, has led me to the conclusion that, for chemical subjects, the analytical method is both too cumbersome and circuitous to be of any real practical use. No person engaged in chemical industry in any capacity—whether workman, foreman, manager, or proprietor—can be taught the prin ciples of chemical science out of his own industry, unless he has some considerable knowledge of general principles to start with. No person who is not grounded in such broad principles can properly appreciate the explanation of the phenomena with which his daily experience brings him into contact, and if his previous training is insufficient to enable him to understand the nature of the changes which occur in the course of his operations, he cannot derive any advantage from technical instruction. These remarks will, I hope, serve to emphasise a distinction which exists between technical chemistry and other tech nical subjects, and I have thought it desirable to avail myself of the present opportunity of calling particular attention to this point, because it is one which is generally ignored in all discussions on technical education. The reason for this difference in the mode of treatment of chemical subjects is not difficult to find. The chemi cal technologist—the man who is engaged in the manufac ture of useful products out of certain raw materials—is, so far as the purely scientific principles are concerned, already at a very advanced stage, although he may not realise this to be the case. The chemistry of manufac turing operations, even when these are of an apparently simple kind, is of a very high order of complexity. There are many branches of chemical industry in which the nature of the chemical changes undergone by the materials is very imperfectly understood; there is no branch of chemical industry of which the pure science can be said to be thoroughly known. For these reasons I believe that I am justified in stating that the chemical technologist