Mr Lahy, A sti^ing electrometer. 113 



on the fibre increased ; the sensitiveness was then 50 divisions per 

 volt. Yet the motion of the fibre was dead beat, and it took up a 

 new position in less than one-tenth of a second. Since the move- 

 ments of a fibre can be readily recorded photographically the 

 instrument seems to promise well as an oscillograph. Further 

 experiments are being made on this use of it. 



It should be recalled that all the above experiments were 

 made with a steady source of potential. Mr H. Darwin has de- 

 signed a new instrument in the light of the experience obtained 

 with this one ; when it is finished more complete tests than these 

 will be made with it. 



I am indebted to Mr Horace Darwin and Mr Whipple for 

 having lent me the string electrometer I used, and for having had 

 certain alterations made in it. I am grateful to Prof. Sir J. J. 

 Thomson for the encouraging interest he took in these experi- 

 ments. 



