168 G. W. Hough on Cataloguing and Charting Stars. 
A clock work mechanism, having a half second’s pendulum 
(p), carries the cylinder (a), 6 in. in length and 10 in. in diam- 
eter; which revolves from west to east, and makes a complete 
revolution every hour. 
4 
rane 
Sj 
Directly over the cylinder is mounted, on a horizontal axis, 
the compound lever (61); to the lower end of which, by means 
