736 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



shaft I is mounted the carrier-arm J, whicli is kept from turning by 

 a spline working in the slot L, and is rigidly connected with the nut 

 (which is 4 in. long) by the screw e d passing through the sleeve and 

 spline and screwing into the nut. M is the feed-wheel mounted on 

 the right-hand end of the feed-screw. N is a lever, the upper end 

 embracing the shaft I, the lower end connected with the projecting 

 arm P of the eccentric, which, by its revolution with the driving- 

 wheel, communicates the necessary vibratory motion to the carrier- 

 arm, as may be seen in dotted lines in the elevation at I. The 

 eccentric can be given any throw within its compass by sliding along 



Fig. 176. 



JSlevation 



the slotted arms of the driving-wheel. The throw may also be varied 

 by connecting the eccentric with the vibrating lever N, at the various 

 points 1, 2, 3, 4, &c. When making a cut, all the parts connected 

 with the shaft I rotate in the direction of the arrow on the feed- 

 wheel M, but in the return stroke the pawl E catches in the teeth of 

 the feed-wheel, and holds it while all the other parts continue the 

 return motion to the end of the stroke ; this causes the screw to turn 

 in the nut, or rather the nut to turn on the screw, and advance the 

 carrier and specimen to the knife. S is a cam embracing the shaft I, 

 and may be set in any position around the shaft, and by its action on 

 the part T of the pawl determines the number of teeth that will be 

 taken at each stroke. 



The feed-screw has twenty threads to the inch, and the wheel one 

 hundred teeth ; the finest feed is therefore two thousand to one inch. 



The two wheels 6 & on the plan and h on the elevation, supported 



