THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[FIFTH SERIES.] 



APRIL 1878. 



XXXVI. Experiments on the Heat-conductivity of Stone, based 

 on Fourier's i Theorie de la Chaleur" By W. E. Ayrton 

 and John Perry^ Professors in the Imperial College of 

 Engineering, Tokio, Japan*. 



[Plates IX. and X.] 



I. 'Wl HEN a body is a good conductor for heat, it is compa- 

 » * ratively easy to find the conductivity correctly by the 

 method employed by Principal Forbes, MM. Despretz, Wiede- 

 mann, Franz, and others, which consisted in observing the tem- 

 perature at different points of a long bar when one end had been 

 kept at a constant temperature sufficiently long for the tem- 

 perature of any one point of the bar to have become constant. 

 But as the substances for experimenting on became less and 

 less conducting, the amount of heat lost by radiation becomes 

 larger and larger compared with that conducted along the 

 bar; so that this method of experimenting fails altogether for 

 a non-conducting substance like stone. 



In such a case the plan usually adopted has been to measure 

 the amount of heat conducted through a very thin wide sheet 

 of the material when the temperature of each of its surfaces 

 was kept constant. But even when considerable precautions are 

 taken to prevent loss of heat from the edges, &c. (such as those 

 employed by Professor Gr. Forbes in his experiments published 

 in the Proceedings of the Royal Society of Edinburgh for 

 February 1873), still we feel sure that the results must be 



* Communicated by the Authors, having been. read before the Asiatic 

 Society of Japan, January 26, 1878. 



Phil Mag. S. 5. Vol. 5. No. 31. April 1878. R 



