92 



MICROSCOPIC ILLUSTRATIONS. 



on discs in this manner, an additional arm for carrying a 

 small black cup, to be placed behind the object, in lieu 

 of the disc, is extremely convenient. 



Description of the Solid Tripod-stand Achromatic 

 Microscope and Engiscope. — This instrument, on its 

 simplest mounting 1 , is represented by the accompanying 

 engraving, fig. 1J. It is in all respects similar to the 

 preceding one, except in its stand. On this account 

 I have placed it in the position in which it is used for 



Fig. 17 



