THE CAMERA LUCIDA. 



129 



THE CAMERA LUCIDA. 



The Camera Lucida, fig. 79, invented by Dr. Wollaston, 

 in 1807, is a valuable addition to the microscopy 

 for making drawings of structures, or for obtaining, 

 with a micrometer, measurements of objects. It consists 



Fig. 79. 



of a four-sided prism of glass, set in a brass frame or 

 as represented in the figure annexed ; and by means of m 

 short tube it is slipped over the front part of either of the 

 eye-pieces, its cap having been previously removed. 

 Mr. Ross attaches the prism, by two short supports, to 

 a circular piece of brass at the end of the tube ; on this it 

 can be slightly rotated, whilst the prism itself can also be 

 turned up or down, by means of two screws with milled 



