556 



Mr. C. V. Boys on Quartz Fibres. [June 14, '89. 



convex, and this magnifies the motion nearly eight times. At the 

 present moment the attracting weights are in one extreme position, 

 and the line of light is quiet. I will now move them to the other 

 position, and you will see the result — the liglit slowly begins to move, 

 and slowly increases in movement. In forty seconds it will have 

 acquired its highest velocity, and in forty more, it will have stopped 

 at 5 feet 8J inches from the starting point, after which it will slowly 

 move back again, oscillating about its new position of rest. It has 

 moved up to and stopped exactly at the division indicated. 



It is not possible at this hour to enter into any calculations ; I 

 will only say that the motion you have seen is the effect of a force of 

 less than one ten millionth of the weight of a grain, and that with 

 this apj)aratus I can detect a force two thousand times smaller still. 

 There would be no difficulty even in showing the attraction between 

 two No. 5 shot. 



And now, in conclusion, I would only say that if there is any- 

 thing that is good in the experiments to which I have this evening 

 directed your attention, experiments conducted largely with sticks, 

 and string and straw and sealing-wax, I may perhaps be pardoned if 

 I express my conviction that in these days we are too apt to depart 

 from the simple ways of our fathers, and instead of following them, 

 to fall down and worship the brazen image which the instrument- 

 maker hath set up. 



[C. V. B.] 



Note. — I have since karnt that in 1841 M. Gaudin melted quartz 

 and drew it out by hand into threads. I have given an abstract of 

 his experiments in the ' Electrical Eevicw ' of July 19th. 



