Thermal Conductivity during the Fusion of Metals. 545 



e and / does not change in any appreciable degree during 

 the melting and solidification of the specimen. R' and R" 



are also similar porcelain tubes protecting iron cylinders 

 A and D. Two narrow holes a\ b' are also radially bored 

 to receive the two junctions of a differential thermocouple, 

 as in the iron piece A. G is a thick iron tube, which 

 serves as an equaliser of temperature, and the interspace 

 between the tube and the porcelain tube R is packed with 

 caolin powder in order to avoid the lateral loss of heat as 

 much as possible. 



The small beating-coil in the cavity between the iron 

 cylinders A and B consists of a nichrome wire 0*5 mm. 



Fur. 3. 



! 



■ 



r 



■ i 



j| 



: i 



• i 



I TTT 



; 



1 : 



iO-rCrn 



thick and about 30 cm. long, wound in a spiral form and 

 well insulated with caolin kit. To the terminals of the coil 

 are fused thick copper leads /, V , which are used as the 

 current and potential leads. The terminal volt and the 

 current passing through the heating-coil are measured by 

 a voltmeter and an ammeter (made by Siemens & Halske); 

 the heat generated in the cavity per unit of time can thus 

 be evaluated. 



The whole arrangement is vertically supported by a 

 porcelain tube R", so as to lie in the middle portion, o£ a 



