1897] 



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 g-lass 

 evolved the machine referred to. He states that, beyond 

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



DESCKIPTION OF FIGURE. 



A. — Microuoiueter 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 the thrust of the 

 wedge 



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

 sary for any degree of cutting, 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, are 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 that of 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 by no means an arbitrary one. For 

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



