HALL AND AYRES. — HEAT CONDUCTION IN IRON. ,295 



The " meau temperature " is the mean between the temperature of the 

 upper stream upon entering the apparatus (as indicated by the ther- 

 mometer Ti in Fig. 2), and the lower stream upon leaving * the apparatus. 

 Neither of these temperatures was taken with great accuracy, aud any 

 one of the mean temperatures given may be wrong to the extent of 0°.5, 



Under K^^ are given values of the conductivity obtained from observa- 

 tions made when the vrarmer stream ran above the disk. Under Ko are 

 given values of the conductivity obtained from observations made when 

 the warmer stream ran below the disk. A' is the mean of K^ and /iTo. 

 In the calculation of the values here given, no account was taken of the 



* The temperature of the lower stream on entering the apparatus was not taken; 

 but the change of temperature within the apparatus was slight. 



