189V] 



MICROSCOPICAL JOURNAL. 



357 



thousand to the inch and more by such an appliance seems 

 almost incredible. 



The inventor, Rev. D. W. Smith, of Brooklyn, N. Y., 

 having- need of some work of this kind to assist him in 

 certain experiments, with a few pieces of metal and glass 

 evolved the machine referred to. He states that, beyond 

 forty or fifty lines to the inch, the task of ruling lies more 



DESCRIPTION OF FIGURE. 



A.— Micronometer screw operating upon the base of the movable wedge. 



B. — Movable wedge, adjusted by set screws working in contact with 

 strips of plate glass. 



C. — Brass block, having only lateral movement caused by (he thrust of the 

 wedge 



D. — Diamond carrier, easily adjusted to any position j.nd weight neces- 

 sary for any degree of cuttiug. and moved laterally by the brass block and 

 longitudinally by hand. 



E. — Graduated drum upon the micrometer screw. 



F, F. — Iron base supporting the entire apparatus. 



The following parts, for distinctness, arc not represented in the figure 

 A broad clamping nut supporting the micrometer screw; an index for the 

 graduated drum; and the retaining springs holding the movable portions in 

 contact. 



in the proper selection of diamond points or crystals, nec- 

 essary for lines of the required fineness, than in the accu- 

 racy of the machine. 



The principle involved is thatof a screw, operating- upon 

 a wedge of brass, moving the latter long-itudinally on the 

 supported bed. The screw contains sixty threads to the 

 inch, which number is b}' no means an arbitrary one. For 

 the wedg-e is capable of adjustment by means of set screws 



