0? THE MICROSCOPE. 29 



be used at once, a considerable range of magnifying power 

 being thus secured. 



Fig. 2. HAND MAGNIFIER SIMPLE LENS. 



The magnifiers shown in Figures 2 and 3 are furnished 

 with what are called diaphragms that is. to say, each one has a 

 thin plate of some opaque material, having a hole of suitable size 

 through its centre. This plate is placed over the lens when 



Fig. 3, HAND MAGNIFIER THREE LENSES. 



but one lens is used, and between the lenses when two or more 

 are employed. It serves to cut off the marginal rays which do 

 not give a clear image, and in this way it greatly improves the 

 definition of the object. 



Two or more lenses, properly adapted to each other, and used 

 together, give results greatly superior to anything that can be 



