330 Effects of Strain on the Thermo-electric Qualities of Metals. 



Number of turns Thermo-electric difference between 



in twisted wire untwisted and twisted copper wire 



per centimetre. in mikrovolt per degree. 



1 0-0054 



3 0-0223 



5 0-0262 



7 0-0419 



8-5 0-0594 



8'5 and partially annealed 0'0345 



14. The effects of twist on the drawn copper wire were also tried, 

 and it was found that 1, 2, 3 turns per cm. in the drawn wire slightly 

 diminished the thermo-electric difference obtained between the undrawn 

 wire and the drawn wire ; but that 4 and 5 turns per cm. in the 

 drawn wire gave the same thermo-electric difference as was found 

 between the undrawn wire and the untwisted drawn wire. 



15. The drawn and twisted copper wire was annealed by putting a 

 gradually increasing current through it till it got red-hot, and then, 

 without breaking the circuit, the current was gradually reduced till 

 the wire was at the temperature of the laboratory. Trying it in this 

 condition along with the undrawn and untwisted copper wire, the 

 current through the hot junction was found to be reversed, being from 

 the drawn twisted and annealed wire to the undrawn wire. The 

 thermo-electric difference was 0-0081 mikrovolt per degree. 



16. Similar experiments on platinoid wires as those described in 

 Section 14 on copper wires gave similar results. Thus 1, 2, 3 turns 

 per cm. in the drawn platinoid wire diminished the thermo-electric 

 difference obtained between the drawn wire and the undrawn wire; 

 but 4 and 5 turns per cm. in the drawn wire gave the same thermo- 

 electric difference (1*477 mikrovolts per degree) as was found between 

 the untwisted drawn wire and the undrawn wire. 



17. The drawn and twisted platinoid wire was partially annealed, 

 and the thermo-electric difference between it and the undrawn platinoid 

 wire was thereby reduced from 1-477 mikrovolts per degree to 0*567 

 mikrovolt per degree. 



18. A beginning has been made of determining the thermo-electric 

 differences between free wires and wires previously permanently elon- 

 gated 1, 2, 3, &c. per cent, by a simple longitudinal stress; also 

 wires while (a) under stress, stretching them within their limits of 

 elasticity ; and (6) under stress, stretching them beyond their limits of 

 elasticity. I hope to be able soon to communicate the results to the 

 Society. 



