on the Thermo-electric Qualities of Metals. 



329 



12. The copper wires numbered 1, 2, 3, of Messrs. Johnson and 

 Matthey were also tried undrawn. 



13. The effect of hardening by twisting has been partially tried. 

 Thus two pieces of laboratory copper wire were taken, and one was in 

 successive experiments twisted 1 turn, 3 turns, 5 turns, 7 turns, 

 8| turns per cm. The wire with SJ turns per cm. got quite brittle, 

 and broke when an attempt was made to put more twists into it. The 

 twisted wire was then heated red hot by an electric current, and 

 allowed to cool. This partially annealed it. 



The results are given in the following table : 



