186 ROYAL SOCIETY OF CANADA 



Conclusion. 

 As can be seen from the curves, in all materials tested, except 

 Aluminium, the ratio of increase per cent resistance to increase per 

 cent stretch is equal to 2+. Manganin and Aluminium in the first 

 parte of the curves show discrepancies, but this is probably due to the 

 unavoidable errors in measurino; such minute changes of resistance. 



j6 



lu 



o 



./6 



O 0-4 oe 12. 16 20 2-» 2a -32 



INCRCflSC PCR C€NT STRCTCH 



Fig 10. 

 In the case of Manganin, when tihese irregularities are omiti.ed, the 

 above ratio has the value 3, but for Aluminium it is a little less. But in 

 the case of the latter thfe wire broke when there was a stretch of only 

 8 cms. in 264; in consequence, the changes of length and of resistance 

 were so small that no general result can be deduced from them. 



