No. 521] SHORTER ARTICLES AND CORRESPONDENCE 303 



There are five objectives, numbered, of which No. 1 is the high- 

 est. The poAver of magnification is as follows : 



Eyepiece and objective 4 = 28 diameters (at 10 inches). 

 Eyepiece and objective 3 = 50 diameters (at 10 inches). 

 Eyepiece and objective 2 = (broken) 



Eyepiece and objective 1 = 330 diameters (at 10 inches). 



The lenses are simple ^aehn»m;«t i>- <l<>uMeN (biting only from 

 the early nineteenth century) and are diaphragmed extensively. 



