THKUMAL CONDUCTIVITIES OP SOME ELECTRICAL INSULATORS. 



457 



Naphthaline. (M.P. = 79 C.) 



The tube was filled by heating to 100 C. in a water bath, and cooling from 

 underneath as in the case of paraffin wax. 



TJ 



CURRENT in Heaters '991 ampere. C* = '982. k r = -00971 



With these results may be compared two obtained by placing a disc of naphthaline, 

 15 centim. thick, between two copper plates and measuring the difference of tempera- 

 ture between the two when a known quantity of heat produced electrically was 

 transmitted (LEES, ' Phil. Trans.,' A, voL 191, p. 416 (1898)). k at 33 C. = '00096, 

 at 62 C. = '00084. 



The somewhat higher values obtained in the older experiments may be due to the 

 fact that the method of producing the disc of naphthaline appeared to develop in it 

 columns of crystals whose axes were perpendicular to the surfaces of the disc and 

 therefore parallel to the lines of flow of heat. 



VOL. cciv. A. 



3 N 



