A Manual Of Photography

200 PRACTICE OF PHOTOGRAPHY. The lenticular image falls on the mirror c, placed at such an angle that it is reflected on the plate of ground-glass d. e is a screen to prevent the overpowering influence of daylight, which would render the picture almost invisible. This form of the apparatus, though very interesting as a philosophical toy, and extremely useful to the artist, is by no means fitted for pho- tographic purposes. The radiations from externalobjects suffer considerable diminu- tionof chemical power in penetrating the lens, and the reflec- tion from the mirror so far reduces its in- tensity, that its action on photographic agents is slow. To obviate the objection of the reflected image, it is only necessary to place the photographic paper in the place of the mirror, but not in an angular position. Tig. 46 represents a photographic camera so constructed in its most simple form: act is the outer box, in which is fixed the lens 6, and c c, another box sliding within it, at the inner enabled to adjust the paper to the correct end of which is placed the prepared paper d: by sliding c e we are focus of the lens, the image being observed through a small hole at e. A great variety of these instruments have been introduced to the notice of students of the art, many of them so unnecessarily expensive that they are beyond the reach of the humble amateur.