34 FERGUSON'S LECTURES. 



LECT. the middle of each bearer ; then through a slit in the 

 v^-v^, middle of the square top (0 and P) of each tower, and 

 going over a small pulley on the top, comes down again 

 the same way, and is at last fastened to the upper end 

 of the socket fixed' in the middle of the above mentioned 

 round plate. These plates S and T have each four 

 round holes near their edges, for letting them slide 

 up and down upon the wires which make the corners of 

 each tower. The balls and plates being thus connected, 

 each by its particular line, it is plain that if the balls be 

 drawn outward, or towards the ends M and N of their 

 respective bearers, the round plates S and T will be 

 drawn up to the top of their respective towers O and P. 

 There are several brass weights, some of two ounces, 

 some of three, and some of four, to be occasionally put 

 within the towers and P, upon the round plates S and 

 T: each weight having a round hole in the middle of it, 

 for going upon the sockets or axes of the plates, and is 

 slit from the edge to the hole, for allowing it to 

 be slipped over the foresaid line which comes from 

 each ball to its respective plate : thus 



The experiments to be made by this machine are as 

 follows : 



1. Take away the bearer M X, and take the ivory 



ball a, to which the line or silk cord b is fastened at 



one end ; and having made a loop on the other end of 



the cord, put the loop over a pin fixed in the center of the 



board d. Then, turning the winch B to give the board 



The pro- a whirling motion, you will see that the ball does not 



pensity of i mme diately begin to move with the board, but, on ac- 



matter to J ,. ,1 



keep the count of its inactt vity, it endeavours to continue in the 

 state it is gtate of regt which it wag in before. Continue turning, 



until the board communicates an equal degree of motion 

 with its own to the ball, and then turning on, you will 

 perceive that the ball will remain upon one part of the 



Note 22. See Engraving, page 33. 



