the paper and object, and when replaced, may be pressed evenly 

 and firmly against the glass by screws (cc) placed at the back. A 

 sliding top covering the glass excludes the light, until it is desired 

 to submit the paper to the action of light, or to protect it from 

 change if kept for a short period without setting. 



CAMERA OBSCURA. 



The Camera Obscura adapted for photographic purposes, is a very 

 superior instrument to that commonly sold under the name. The 

 lens may be either achromatic or miniscus. 



WILLATS'S IMPROVED CAMERA, (Fro. 2,) 



Which may be used for any photographic purpose, is a box, in 

 the front of which the lens is bedded, by which an increase of 

 light is obtained, the quantity admitted being regulated by a 

 diaphragm, having apertures of different diameter. The back part 



Fig. 2. 



of the camera slides into the front, and to secure a very accurate 

 adjustment, is mounted with a screw. It is moved in or out by 

 turning a small handle at the back. The frame with the ground 

 glass (Fig. 3) is furnished with a moveable top and sides, which 

 when extended, exclude the light, and aid the operator in deter- 

 mining the best focus. 



