THERMAL CONDUCTIVITIES OF SOME ELECTRICAL INSULATORS. 



159 



Ice. 



Obtained by filling the brass tube with air-free distilled water and slowly freezing 

 it from below upwards by inserting the base of the tube into liquid air. 



T> 



CURRENT in Heaters T989 amperes. (7 = 3'956. k v = -0391 - 



With these results may be compared the following values : 



F. NEUMANN, 'Ann. Chim. Phys.,' 3, p. 66 (1862), k = -00568. 

 MITCHELL, 'Proc. Roy. Soc. Edin.,' 86, p. 592 (1885), k = '005. 

 It will be noticed that the conductivity of ice near its melting-point is between 

 three and four times that of water, which H. F. WEBER has found to be '0012 at 

 4 C. and several observers have found to be about '0014 at 20 0. 



3 N 2 



