on 



Rods of Iron, Nickel, and other Metals 



395 



Fisr. 7. 



it respond to 1000 vibrations per second, and record its move- 

 ments clearly on the moving surface of the chronograph. 

 The diagram (fig. 8) shows how the torsional magnetic 

 stylus is constructed. 



Fisr. 8. 



A B. The long solenoid, shown broken to save space. 



D. The twisted wire of iron. 



S. An aluminium pointer, which is adjusted to touch the 

 smoked glass plate of the chronograph. 



Repeated tests show that the " latency " of this new form 

 of stylus is exceedingly minute ; this fact will, I believe, 

 make the instrument very useful for getting accurate chrono- 

 graphic measurements. 



26. I also found that when the stylus is connected, by means 

 of a thread or fine wire, to a mica' tympan T, true telephonic 



