318 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



adjustable by means of a screw with a large milled head. By bending 

 the joints, the lens may be brought near the pillar for use in connec- 

 tion with tlie bull's-eye ; or by attaching the jaws or ring to a longer 

 wire, the total ai-m-leugth may be increased at will. At the end of 



Fig. 68. 



the arm is a vertical pivot, upon which 

 can be slipped almost any kind of 

 pocket magnifier. Or, the lenses being 

 removed, a split wire may be inserted 

 into the hollow end of the arm, bearing 

 a pair of hinged semicircular jaws 

 (shown in the fig.) for carrying an en- 

 graver's glass or any variety of large 

 lenses not requiring delicate adjust- 

 ment. For magnifiers of higher power, 



requiring more precise adjustment, a ring is substituted for the 



jaws. 



There is a fine adjustment at the top of the rectangular frame, 



where a screw with milled head, pressing the pillar against the 



Fig. 69. 



spring, promptly but steadily depresses the^lenses to the extent of 

 about four times its own motion. 



Simplicity can hardly go further than in J. W. Queen & Co.'s 



