Camps of Exercise. By Col. J. LE COUTEUR, A.D.C. to the Queen. Musketry Instruction for the Cavalry Carbine and Pistol recently issued to the French Cavalry; with suggestions for the Training of Cavalry, and its important Function in future Battles. By Lieut. A. STEINMETZ, Queen's Own Light Inf. On a Model illustrating the Parabolic Theory of Projection for Ranges in Vacuo. By 454 . 497 . 502 The Rigging of Large Screw Vessels. By Commander W. HORTON, R.N. England, her Wars, and Expeditions, since 1815. By Colonel ADAIR, A.D.C. to . 509 521 560 On Improvements in Helmets and other Head-dress for British Troops in the Tropics, more especially in India. By JULIUS JEFFREYS, Esq., F.R.S. Irregular Troops. By Captain G. M. MACAULAY, Commandant 1st Scinde Horse Proceedings of the Thirty-first Anniversary Meeting Address of the Right Hon. Sir GEORGE CORNEWALL LEWIS, Bart. M.P. χχίν xxix Page 391, 3rd and 4th lines, for "four years," read "four winter months." Page 392, 1st line, for "in France," read " at Brighton." In the List of Members, the name of Captain A. B. HAWES, Bengal Army, should be entered as a Life Member, and not as an Annual Subscriber. hour which is allowed me, and beyond which I hope I shall not draw on your patience, to explain as clearly as I can the general principles of photography, an art which is every day rapidly extending, and the aid of which may, I believe, be usefully enlisted in many secondary military operations. In speaking of photography as an art, it must be understood that I do not wish to tread on the delicate ground of its status as a fine art, but I am employing the term art in its wide general signification, viz. the execution of works of all kinds. Our power of executing a photograph, or indeed any work, depends on our taking advantage of certain powers in nature which produce certain effects. The relation between these powers or causes and their effects, it is the province of science to investigate-to deduce and establish the fact of a certain sequence of events, or what we term the laws of nature; and then the same truth, which is a principle in science, becomes a rule in art. In addressing you on the subject of photography, there are then two wholly distinct points of view from which I may look at the subject. Either I may consider the scientific principles on which photography rests, and how these truths are the rules of our art; or I may direct your attention to the application only of our rules to the production of photographs, paying little heed to their existence or general truth as principles. As, for instance, in regarding the steam-engine, we might, on the one hand, examine the mechanical principles and physical laws on which the machine works; or, on the other hand, we might confine our attention to the details of construction, or the stoking and driving. I have preferred, and I hope I am justified in so doing, the former course; I believe it will be more interesting generally. Both are equally important; indeed the latter, the examination of details, is perhaps the most important, as we cannot produce a photograph, with a perfect knowledge of principles, without a thorough knowledge of details; but at the same. time it would be impossible in one lecture to treat of both. The details are most fully given in many hand-books on photography, such as Hardwich's, and given from the result of experience ten times greater than I can boast of, and far better than I can give. But at the same time from the aim of these works-to enable the reader to become a practical photographer-it is difficult to obtain at first a general knowledge of the principles from them, as the statement of the principles is constantly interrupted by a description of manipulative details. I have, therefore, disregarded these details: it would be very wearying and quite useless, to give a number of photographic formula without at the same time actually manipulating a photograph; while I hope a slight general knowledge of the principles may be interesting and useful to many officers, if at any time they wish to take up the subject practically. In conclusion, I propose to mention some applications of photography to military purposes: these are at present not very numerous; but these instances will, I trust, protect me from the appearance of assumption in lecturing on a subject which many non-military photographers who have paid it far greater attention would be better able to handle. I have undertaken the subject with great hesitation, and only because I believe that it may often be applied with great advantage to the service. Photography includes all processes in which pictures are taken by the action of light. These processes are very numerous: in some different substances are used for the sensitive film, in others the same substances are employed under different conditions. As it would be very confusing to revert from one to the other, I propose taking the ordinary or most generally employed process as a type, and explaining it. We will therefore take the wet collodion process, and its accompanying printing process on paper. It is not my intention to assume that you know anything of photography, and as there may be some present who have never watched a photograph being taken, I may be permitted to define, as it were, what I am going to explain, and roughly to show the various stages of a photograph: the effect of each step I hope afterwards to explain. I have here a camera. It must not be fancied that there is any peculiar photographic action or virtue in a camera. I cannot now explain |