APOCHROMATIC LENSES 



35 



Apochromatic Objectives. 



Compensating Eye-pieces for English Bodies. 

 248 12 18 27 



It is of interest to note that Mosi-s. Powell and Lealand have 

 since produced a remarkable lens on the same system, having a N.A. 

 of 1-50, with a, power of jV 11 of an inch. Object-glasses are also now 

 made by other makers, English, European, and American, those 

 having fluorite in them being termed apochromatic, while others 

 made "of new kinds of glass are called semi-apochromatic. Senii- 

 apochromats are being daily improved, so much so that some recent 

 objectives nearly equal apochromatic objectives themselves. 



