A MANUAL OF PHOTOGRAPHY FOUNDED ON HARDWICH'S PHOTOGRAPHIC CHEMISTRY BY GEORGE DAWSON, M.A., PH.D. LECTURER ON PHOTOGRAPHY IN KING'S COLLEGE, EIGHTH EDITION LONDON LONDON J. & A. CHURCHILL, NEW BURLINGTON STREET PREFACE. НЗ 7873 Ir will be necessary to make a few remarks by way of Preface to this edition of Mr. Hardwich's treatise on Photography. The short compendium of general Chemistry has been omitted, because this Science can be better studied from the more comprehensive works on that subject which now abound. Indeed, a knowledge of Chemistry is not essential to the practical Photographer, for it is only on very exceptional occasions that he will be called on to prepare any of his own Chemicals. At the same time it is deemed desirable to give a Vocabulary, mentioning the nature and properties of the various substances used in Photography, except when these are described in the body of the work. Further it will be observed, that all Hypothetical speculations, or suppositions, respecting the action of Light on certain bodies submitted to its influence, have been expunged. Sometimes when an undoubted explanation could be given of certain phenomena, that explanation has been made so far as is consistent with well ascertained facts. The main object of the Editor has been to give practical instruction in our fascinating art, to lead up the novice from first principles to the higher M291956 branches, and to impress the value of care and exactitude in every operation. A considerable portion of Mr. Hardwich's practical instructions have been retained, simply because the Editor could not improve upon such examples of clear description and minute detail. For the rest, he is content to rely on the verdict of his brother Photographers. The Editor takes this opportunity of acknowledging his great obligations to several gentlemen for valuable hints, and to others for material assistance in the treatment of subjects with which they are more familiar than himself. KING'S COLLEGE, February, 1873. GEORGE DAWSON. ? |