692 HENRY A. KOWLAND 



seen to cross the lines at right angles, corresponding to the points of 

 intersection of the two sets of rulings. This pattern resembles closely 

 in appearance that of watered silk. The corrector of the machine is 

 adjusted until this undulatory pattern is as regular and has as small 

 an amplitude as possible. 



Any description of Eowland's dividing engines, however brief, would 

 be incomplete without some mention of Mr. Theodore Schneider who 

 for twenty-five years was Professor Eowland's mechanician and assistant 

 and who died only a few weeks before him. It was he who made the 

 screws and most of the working parts of the machines, and it was he 

 who superintended the ruling of every grating that has left the Physical 

 Laboratory of the Johns Hopkins University for use elsewhere in the 

 world. 



GENERAL DESIGN OF DIVIDING ENGINE* 



The object of this machine is to rule straight lines on metal or glass 

 surfaces, exactly parallel and at exactly equal distances apart. The sur- 

 face to be ruled is attached to a frame which is moved forward by a nut 

 as it is advanced by a screw; the ruling edge is generally a diamond 

 mounted in such a manner as to be drawn to and fro across the surface to 

 be ruled, but to be in contact with it during <only one of these motions. 



Kotary motion is imparted to the main shaft (48 A) by means of a 

 driving pulley, operated by a belt attached to a water motor (not shown 

 in the cuts). Mounted on the main shaft are the cams (46, 47) for 

 operating the pawl-levers, which turn the screw and advance the nut; 

 the cam (55) controlling the mechanism for raising the diamond; and 

 the crank (50) which by means of the connecting rod and cross-head 

 impart a reciprocating motion to the ruling carriage and its diamond. 

 By means of adjustments in the crank and connecting rod, the length 

 of stroke of the diamond may be varied, and rulings of different lengths 

 are thus obtained. 



In each revolution of the main shaft, the cycle of operations that occur 

 is as follows: Let the diamond be on the plate in a position to begin 

 ruling. It is moved forward, i. e. toward the shaft, by means of the 

 ruling frame and parts described, and a line is ruled. The stroke of 

 the engine being now about to reverse, the cam controlling the mechan- 

 ism for lifting the diamond performs its duty; and, while the engine 

 is on its return stroke, with the diamond off the plate, the latter is 



2 The figures in the text refer to the numbered parts in the cuts which follow the 

 article. 



