Manchester Memoirs, Vol. xliii. (1899), No. 8. 5 



during the time T, and indicating it by z'l, ^o, &c., we 

 have : — 



a similar equation with Vi,Vo,Ui, Uo and / accented, holding 

 for the other disc. 



If ^ is the mean rate of generation of heat in the 

 heating coil embedded in the middle steel disc, v-^ and v{ 

 the temperatures of the two halves of the disc, M its mass, 

 C its specific heat, vS its surface and k its emissivity, the 

 mean heat transmitted per second to the discs of material 

 under test 



= 11 ( mean — ^ + mean — - ) - ^h— 



2 \ at at ) 2 



Hence 



= 7rr^M 



or 



ff-A 



f( 



6* 47rr/\- Trrt- 



I MC 2'!vrhpl\ J J 2iv}^cpl j-j- \ 



I /J/C 2Trf^cp^' \ j^, 2irr'cpl ' jj, ^ 2 ) 

 V 2 6 J ^ 12 " j 



