on Rods of Iron, Nickel, and other Metals, 389 



into a glass tube when melted. If the glass tube be kept hot 

 during the formation of the casting, and be cooled slowly, 

 very long rods may be produced, in some cases 25 centim. 

 long. The glass tube is removed from the metal by being 

 cracked. When treated as the iron rods were in the previous 

 experiments, no movement whatever could be perceived. 

 From the brittle nature of Bi it could be subjected to only a 

 slight amount of torsion. 



13. A transitory current of electricity induced in a magnetic 

 core subjected to permanent torsional set. 



Diagram of Connexions, &c. 



A B. A long helix of covered copper wire 30 centim. long, 



2100 coils, mean area 0*5 centim. 

 C D. A rod of annealed iron 4 millim. diam., 30 centim. 

 long. 

 G. Low-resistance galvanometer, astatic needles (con- 

 structed for ballistic work by Elliott) . 

 P. Current-reverser. 

 K. Key. 



E. Battery (2 E.P.S. accumulators). 

 R. A resistance-box. 



F. Amperemeter. 



The galvanometer was so placed that it was in no way 

 affected, either by the helix A B or by the magnetic action of 

 the core. 



14. When the iron core C D was freshly annealed, and free 

 from magnetization, except that produced by the inductive 

 action of the earth's magnetizing force, a current was passed 

 through the helix ; a transient current was indicated by the 

 galvanometer as existing in the circuit of which the iron core 

 formed a part. The current produced a deflexion of 150 

 divisions of the scale ; a Rowland inductor circle in the 

 earth's horizontal field gave 300 divisions. (The log. of the 



