Even more significant is the manner in which photography, Qince the invention of the dry film, has extended its operations fin. the advancement of science, and for the delight and instruction of every class of the community. The most ordinary photograph is a record of something, stimulating the faculty of observation, memorising for future use more than can be perceived at a casual glance. Architect and engineer obtain by its aid more accurate and useful ideas of buildings and machinery than could be conveyed by any but the most laboriously prepared drawings. A weekly report of work in progress may be comprised in one or two snapshots. Scarcely less useful is the camera in the hands of the detective, or the medical specialist. Its revelations of wild nature in its living haunts are the delight of the naturalist; the astronomer finds it indispensable ; and in connection with the X-ray's the dry plate has even introduced the scientific investigator to a knowledge of the unseen.
Thanks to the dry plate we find in our daily newspapers faithful pictures of events that took place only a few hours before. We can step into a cinematograph theatre and see these happenings in their actual details and surroundings, with all the living movements, just as if we were present at the time and place of their occurrence. It is safe to prophesy that, in the course of a few years, satisfactory photographs in the veritable colours of nature will be an everyday matter ; without the dry plate not one of the many steps already reached in this direction could have been attempted.
Most of the creators of modern photography are still with us, and it is invidious to particularise. The roll of honour would have to be a very long one, and in the attempt to compile it, some would certainly be forgotten who ought to be found inscribed upon it. We only dare mention here the veteran Sir W. de W. Abney, whose investigations in almost every branch are invaluable, and who may specially be termed the father of the many processes involving the bichromates ; Dr. J. M. Eder, the famous chemist and inventor of many new developers ; Mr. W. Willis, who with Captain Pizzighelli perfected the platinotype process ; and Sir J. W. Swan, who rendered the carbon process popular. So fascinating a study was certain to attract the attention of the greatest minds ; each has been content to add his own contribution to the general fund of knowledge, often without seeking for any recognition or reward beyond the pleasure incidental to the pursuit itself.
The question is often asked, What is Photography ? Ought it to be described either as an art or a science ? Many will contend that, setting aside the gum-bichromate and oil processes (in which the photographic image becomes little more than a basis for the work of hand and brush), a photo graph is a mere mechanical reproduction from first to last.
True it that manufacturing enterprise has so simplified each stage and so perfected apparatus that the beginner may produce a passable print, by just pressing a button, and follow ing certain prescribed directions with ready-made solutions. But this does not affect the claim of photography in the hands of its more qualified exponents to a place among the recognised pictorial arts. Art has been defined as nature interpreted by the individual. Like other arts photography has its limitations. But in the selection and arrangement of his subject, variation of exposure, manner of development, etc., there are opportunities for the specialist and even for the genius. Two operators given the same point of view may produce vastly different results, and yet each be meritorious. That there are mechanical operations must be admitted, but throughout they are capable of control and may be influenced to produce the effect which the craftsman has in view. Work of the kind we refer to entails as much judgment, originality, and patience as a water-colour painting and has almost the same conventional restrictions ; differing from the latter very little except that copies, by means of the original negative, may be more easily obtained.
On the other hand the photograph need not always be a faithful representation of existing fact. We have known a few heaps of sand on a kitchen table, with the artful aid of flour dredger, some moss, and a toy chalet, become a very characteristic example of Swiss Alpine scenery when interpreted through the camera. An ingenious piece of apparatus, called a duplicator, enables the plate to be exposed in two successive portions with very startling consequences. We do not feel justified in deciding that there is no such thing as a genuine " spirit " photograph : but experts seem unable to devise any test which cannot be evaded by those who are bent on proving that these manifestations are not supernatural in character. The photographs submitted in evidence by the two contending parties in litigation about " ancient lights " have been known to differ considerably as regards the apparent proportion of adjacent buildings. All these may be deliberate sophistications. With the best intentions the photographer will sometimes find that his result does not convey an exact idea of his subject ; and that indeed instruments of precision and a worker of scientific knowledge are required in order to obtain accuracy of this description.