138 



Dr. J. Monckman. The Specific 



larger ones, D mica. The exposed ends were filed flat, and fit loosely 

 into the tube D. The dimensions are: length, 30 mm.; width, 

 3f mm. ; distance, 7 mm. between the free ends, a, b. 



The change of resistance was so great and fell so quickly at the 

 higher temperatures that it gave rise to a suspicion that the increase 

 of conductivity might arise from particles of the rods being torn off 

 and mixed with the sulphur. To test this, the rods were placed in a 

 second tube of boiling sulphur, so that when placed in the tube of 

 pure sulphur they might not reduce the temperature of the liquid. 

 After removing and allowing the adhering liquid to flow back, they 

 were placed in the other vessel, and the current passed at once. The 

 deflection was the same as before, and steady, neither did the rods 

 appear to be acted upon in any way. 



Hence we concluded that the change was in the sulphur itself. 



Resistance. — Ordinary roll brimstone : — 



Eeduced to one standard 



Temperature. Potential. Deflection. by multiplying by 60/?;. 



440° 2£ 60 1560 



300 „ 12-5 325 



270 „ 2 ........ 52 



250 „ 1 26 



250 55 10 24 



223 3 7 



195 60 6 6 



150 „ 5 5 



140 „ 2 2 



125 „ 0-5 0-5 



Another specimen gave slightly different numbers, but of the same 

 order. 



With precipitated sulphur the resistance was considerably 

 higher. 



440° 4-1 35 512 



350 „ 5 73 



335 3 44 



335 8-2 7 51 



290 54 5 5-5 



280 „ 2-5 2-8 



260 „ 0-5 0-55 



125 could get up a. .' . . . . 



The specific resistance may be calculated from these tables, using 

 the quantities previously given, namely, 1. 30 mm., w. 3f , d. 7 ; and 



