On the Electric Conducting Power of Thallium and Iron. 543 



together with the formulae for the correction of the conducting 

 power for temperature of the different specimens, were : — 

 For Mr, Crookes's metal, 



1st wire. 2nd wire at 0°. 



A=9*364-0*037936£+0*00008467£ 2 ; 9*169. 



For M. Lamy's first specimen, 



2nd wire at 0°. 3rd wire. 

 A=9*419-0*039520*+0*00009656* 2 ; 9-082; 9*223.. 



Second specimen, 



2nd wire at 0°. 

 A = 9*054-0*034697£+0*00006554* 2 ; 9*226 ; 



or as mean of all the determinations, some of which are not given 

 here, 



\=9*l63-0*036894£ + 0*00008104£ 2 . 



The conducting power of thallium therefore decreases between 

 0° and 100° 31*420 per cent., which is a larger percentage decre- 

 ment than that obtained for many other pure metals, namely 29*307 

 per cent.* 



Iron. — The specimens of iron experimented were, with two excep- 

 tions, lent us by Dr. Percy. In the following Table we give the results 

 obtained with them : — 



(1.) Electrotype iron, deposited from solution of pure sulphate of 

 iron. The strips were very thin and porous ; we could not 

 therefore obtain concordant values for the conducting power, 

 but we were able to determine the percentage decrement in the 

 conducting power between 0° and 100°. We have, for the above 

 reason, taken the first observed conducting power equal 100. 



X= 100-0*51 182£+0*0012915* 2 , 

 corresponding to a percentage decrement of 38*262 per cent. 

 (2.) No. 1, annealed and cooled in hydrogen. 



X= 100-0*51894^ + 0-0013415^, 

 corresponding to a percentage decrement of 38*479 per cent. 

 (3.) Electrotype iron, a strip cut from the same foil as No. 1. 

 \= 100-0*51355^+0*001322 H 2 , 

 corresponding to a percentage decrement of 38*134 per cent. 

 (4.) No. 3, annealed in air. 



\=100-0-50895£ + 0*0002735* 2 , 

 corresponding to a percentage decrement of 38*160 per cent. 



(5.) This, as well as Nos. 6, 7, 8, were specimens of iron which have 



been analysed. They were all hard drawn. 



X=15*719-0-074370f + 0*0001763^, 



corresponding to a percentage decrement of 36*070 per cent. 

 (6.) \ = 15*672-0*074045* + 0*0001761* 2 , 



corresponding to a percentage decrement of 36*010 per cent, 



* Phil. Trans. 1862, Part I. 



