In adding a volume on Photography to the Concise Knowledge Library, we have felt that we were dealing with a subject which can only be approached through the avenues of actual practice. This is true about photography, even from the historical point of view. In the beginning it was sponsored by the highest scientific authorities of the time, and leaders of science, from Faraday to Lord Rayleigh, have given of their best to bring it to its present state of perfection. And yet its fundamental processes have to be taken for granted. No chemist by taking thought could have evolved them; they were stumbled upon accidentally by empirics, and it has puzzled the scientific world ever since to explain them adequately.

Similar considerations apply to the popular study of photography. Its results may give pleasure to the million; its methods interest only those who practise them. When we take up a volume on natural history, for instance, we do not necessarily expect to find detailed instructions how to capture wild animals or how to prepare them for the table. But the reader of a work on photography is an actual, or at least prospective, owner of a camera. And this, not merely because the hobby has acquired so widespread a popularity, but because its joys and mysteries are reserved for those who have crossed the threshold of the dark room.

The Concise Knowledge Photography should enable the student to arrive at a creditable proficiency in each department, and suggests the works most suitable for his perusal should he afterwards aspire to become a specialist. The directions have been carefully thought out with a view to meet all ordinary contingencies, but it is obviously impossible to provide against every incidental source of error. One of the virtues of photography as an educative pastime is that it stimulates the observing and reasoning faculties. To cite an example, he who essays the gum bichromate process and uses a brush to spread the sensitised gum will, it is hoped, recollect that the substance which becomes insoluble on the paper will ruin his brush, if he allows it to dry unwashed. The formulae selected are those which experience has proved to be useful. Some old friends may be missed, but, we hope, not regretted; amongst them the uranium intensifier, and that cheap but unreliable method of toning printing out papers by adding a mineral acid to the fixing bath.

One sad destiny awaits every work on photography. It will, all too soon, cease to be up-to-date. Just as we are preparing for press, Dr. Mees and Mr. Welborne Piper have communicated to the Royal Photographic Society some hitherto unrecognised facts regarding hydroquinone developers. While sulphite has been proved a source of fog with this particular agent, it appears that a developer containing only caustic soda and hydroquinone, provided the latter is in large excess, will give soft gradations with comparatively under-exposed plates. A useful variation of Dr. Eder's rehalogenation formula on page 192, has just been introduced, in which ammonium chloride is substituted for the bromide. This formula may also be applied for softening and toning bromide or gaslight papers. Fortunately for the reader who wishes to keep abreast of the times, the photographic press is exceptionally well conducted, and the latest information will be found summarised in the current British Photographic Almanack. As long as we possess a bookshelf the volumes of this almanack will find an honoured place thereon. We had reason to prize them as a reliable source of information in the old days, when books on photography were few and far between; although we must not forget Mr. E. J. Wall's excellent Photographic Annual.

The appointment of Sir Benjamin Stone as official photographer for the Coronation of King George V., must not pass unnoticed here. This is almost the first public recognition of photography for the purposes of historical record.

By the kind permission of the editor of the Photographic Journal, we are enabled to include photo-micrographs of the principal screens employed in screen-plate colour photography, and also the diagrams of Mr. A. E. Salt's shutter-testing apparatus, both having originally accompanied lectures or communications to the Royal Photographic Society. The view in New York, by Mr. Alvin Langdon Coburn, appears by the courtesy of Messrs. Duckworth, the publishers of New York. Full of atmosphere and originality, this study serves to prove how well adapted is a camera picture to receive the impress of a vigorous and poetic mind. It not only tells us of the towering mass of the Park Row Building, but also suggests effectively the enterprise and industrial forces at work in the great modern city where it sprang into being.

In the selection and arrangement of illustrations we have been fortunately able to depend throughout on the advice of Mr. Roger Ingpen. We must also thank the many contributors and others who assisted in the work of revising the proof sheets, and trust that such technical errors as escaped correction are neither numerous nor important.

A Flower Study. Frontispiece.

A Flower Study. Frontispiece.

W. H Rogers. A Woodland Path.

W. H Rogers. A Woodland Path.