Titanium, and Vanadium by Thermelectronic Currents. 245 



room temperature is on the average 0*0214 



ohm 



They 



must be free from flaws, and it is further most essential 

 that the two faces be as nearly as possible plane and parallel 

 to each other, no deviation of more than 0*01 mm. being- 

 admissible. Any appreciable deviation in thickness will, 

 especially at the higher temperatures, reveal itself imme- 

 diately by the plates burning through instantly at the weak 

 place. 



The plates are either mounted in a special furnace arrange- 

 ment to be described in a later paper, or simply clamped 

 between bars of graphite in the following way : — two rect- 

 angular nieces of graphite A and B (fig. 1) from 7 to 8 in. 

 long, 2 j in. wide by 1 in. thick, are cut down at one extremity 



Fiff. 1. 



Carborundum powder 



Method of mounting- graphite plates. 



in such a way as to leave protruding, level with the upper 

 surfaces, circular rods C and D of \ in. diameter and 2*5 in. 

 in length. The free ends of these rods are provided with 

 horizontal slots, 0'5 in. long, into which the extremities of 

 the thin graphite plates fit tightly. The object of these long 

 rods is to reduce the loss of heat due to conduction, which 

 becomes very serious when the heated plates are in direct 

 contact with the voluminous bars A and B. These bars 

 communicate through an ammeter and an adjustable re- 

 sistance with a battery of accumulators. A voltmeter, by 

 means of which the drop of potential along the plates can 

 be ascertained, is shunted across A and B. In order to 

 provide the necessary space below the heated plate for the 

 full development of the luminous phenomena, the bars A and 

 B are laid upon wooden blocks E and F, and the whole 

 apparatus is supported by a brick. The graphite plates to 



