ACHROMATIC OBJECT-GLASSES*. 

 For the 1st & 2nd Class Stands (Nos. 1, 2, 3 & 4). 



The increase of the angle of aperture of the Object-Glasses in the 

 following Table is more especially worthy of notice in the lower powers, 

 which, adjusting through considerable thickness of glass, or some depth 

 into water, will, with a large aperture, exhibit those objects which are 

 the most frequently examined by the naturalist, with a definition that 

 a smaller angle of aperture cannot give. One of these Object-Glasses, 

 a 4-10ths (erroneously called " half-inch"), is thus alluded to in the 

 "Reports of the Juries of the Great Exhibition" (p. 266), Class X., 

 No. 253. 



"The half- inch focus of 70° aperture is a wonderfully fine combina- 

 tion, easily showing objects considered difficult for a one-eighth 

 inch focal length a little more than a year since, and bearing 

 the application of the higher eye-pieces in an unprecedented 

 manner." 



The Erecting Glass for low power £1 



The magnifying power of this glass with the 2-3rds Object-Glass 

 and employing eye-pieces Nos. 1 & 2; is from 5 to 150. 



* These Object-Glasses can be adapted to Ross' or Powell and Lealand's 

 Microscopes without the instruments being required for that purpo>e. 



