CONTRIBUTIONS TO SCIENCE. 



511 



the four series of waves above mentioned, except that the 

 balls describe circles instead of ellipses about their mean 

 positions. We give the description as printed in the essay ; 

 the apparatus itself is in the Cavendish Laboratory. 



The instrument stands on a pillar A (Figs. 7 and 8), in 

 the upper part of which turns the cranked axle CO. On the 

 parallel parts of this axle are placed two wheels, RR and TT, 

 each of which has thirty-six holes, at equal distance, in a circle 

 near its circumference. The two circles are connected by thirty- 

 six small cranks of the form KK, the extremities of which turn 

 in the corresponding holes of the two wheels. The axle of the 

 crank K which passes through the hole in the wheel S is bored 



Fig. 7. 



Fig. 8. 



so as to hold the end of the bent wire which carries the satellite 

 S. This wire may be turned in the hole so as to place the 

 bent part carrying the satellite at any angle with the crank. A 

 pin P, which passes through the top of the pillar, serves to pre- 

 vent the cranked axle from turning ; and a pin Q, passing 

 through the pillar horizontally, may be made to fix the wheel R 



