ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



511 



optic field, so as to leave it quite free. For use with this illuminate] 

 (fig. 106) a lens of 35 rum. diameter, and 72 mm. focus, is recommended. 



Fig. 106. 



Bausch and Lomb's Improved Form of Camera Lucida.* — The 

 construction of this camera lucida (fig. 107) presents a number of im- 

 provements over older forms, although retaining the original optical 

 principle. The Abbe prism is mounted in a closed box provided with a 



Fig. 107. 



rotating disc carrying a series of dark glasses of different shades. These 

 glasses come between the prism and light from the Microscope eye-piece, 

 and serve to moderate its intensity. A similar series of coloured glasses 

 is arranged to moderate the light coming from the mirror. With the 



Catalogue A, 1904 (Microscopes and Accessory Apparatus) p. (JS. 



