544 Royal Society : — 



(7.) \=14-269-0-064133* + 0-0001456**, 



corresponding to a percentage decrement of 34*742 per cent. 

 (8.) X = 12*342-0055894£+0*0001379* 2 , 



corresponding to a percentage decrement of 34*117 per cent. 

 (9.) Strip of iron, heated in a current of hydrogen at a red heat for 



two hours. This, as well as Nos. 10, 11, 12, were hardened. 

 X = 14*673-0*067999£+0*0001597* 2 , 



corresponding to a percentage decrement of 35*459 per cent. 



(10.) As No. 9, heated for three hours under sugar charcoal in a 

 current of hydrogen ; the carbon taken up was 0"99 per cent. 



X=10*654-0*044560* + 0*00009789* 2 , 

 corresponding to a percentage decrement of 32*637 per cent. 



(11.) As No. 9, heated for four hours under sugar charcoal in a 

 current of hydrogen; the carbon taken up was 0*933 per cent. 



X=9*925-0*040097* + 0*00009168* 2 , 

 corresponding to a percentage decrement of 31*163 per cent. 



(12.) As No. 9, heated for three hours under sugar charcoal in a 

 current of hydrogen; the carbon taken up was 1*06 per cent. 



X=9*457-0*037573£ + 0*00008642*! 2 , 

 corresponding to a percentage decrement of 30*592 per cent. 



(13.) Thin music wire, melted with one quarter of its weight of 

 peroxide of iron under a flux of plate glass. 



X= 13*381 -0*056829^ + 0*0001230^, 

 corresponding to a percentage decrement of 33*278 per cent. 

 (14.) A piece of narrow watch-spring. 



X=8*565-0*029099* + 0*00005383f, 

 corresponding to a percentage decrement of 27*689 per cent. 

 (15.) Commercial iron wire. 



X= 13*772-0*058970^ + 0*0001242^, 

 corresponding to a percentage decrement of 33*801 per cent. 

 From the results obtained, it is obvious that the higher the cor 

 ducting power the higher the percentage decrement in the conducting 

 power between 0° and 100°. This has been proved to be the case with 

 about 100 alloys with which we have experimented. We have als( 

 found that we may deduce the conducting power of a pure metal fron 

 an impure one when the impurity does not reduce the conducting 

 power more than, say, 10 to 20 per cent. According to our experi- 

 ments, the percentage decrement in the conducting power of ai 

 impure metal between 0° and 100° varies in the same ratio as the 

 conducting power of the impure metal at 100°, compared with tha' 

 of the pure metal at 100°. 



Thus, from specimens Nos. 5, 6, 7, 9, 13, and 15, the conducting 

 power of pure iron was found to be at 0°= 16*725. 



In conclusion, we give the values found for specimens of c alt 

 and nickel wire lent to us by Professor Wohler. They were a 

 follows : — 



