28 



ELEMENTARY PHOTO-MICROGRAPHY. 



the fine adjustment, and the coarse adjustment is 

 done by sliding the object carrier (fig. 2). 



It will be noticed that in fig. 2 a short tube A 

 is shown, though such is not necessary for ordinary 

 low power work ; but it is a decided advantage to 

 be able to use accessories, such as iris diaphragm, 

 polariscope, spot lens, and substage condenser, all 

 of which may be slipped into this tube, thereby 

 extending the field of operations considerably. 

 Such a tube is known as an adapter, and may be 



FIG. 2. 



FIG. 3. 



- e - 



FIG. 6. 



