144 



Dr. J. Monckman. The Specific 



that only pure soluble sulphur should be used, and that great care 

 should be taken not to raise the temperature in melting it so high as 

 to produce any of the insoluble modification. 



Two rectangular graphite rods were placed parallel to each other, 

 the one projecting about an inch at one end, the other at the other 

 end. 



The edges were turned towards each other, as shown in the figure, 

 leaving a space of one millimetre, which was filled with melted 

 sulphur. This was levelled off with a hot iron to make the portion 

 between the corners as thin as possible. 



When one of the projecting ends was placed in contact with a 

 charged electroscope, the other being to earth, the charge fell more 

 quickly when illuminated, on the average as 5 is to 4. 



As little reliance can be placed on these experiments, a quadrant 

 electrometer was charged, and the graphite rods, separated by sulphur, 

 inserted between the binding screws, so that the negative quadrant 

 was connected with the positive one through the sulphur (T5 cm. long, 

 1 mm. thick, and 1 mm. broad). 



The electrometer was charged to the same potential in each experi- 

 ment in a series and allowed to run down for a certain time. Sun- 

 light was allowed to fall on the sulphur, but shaded from the rest of 

 the apparatus ; when not required the ordinary window blind was 

 drawn down. 



Of course the electrometer and sulphur were protected from induc- 

 tion by surrounding bodies by wire screens. 



The following three series of readings were taken on different days, 

 and in one or two cases clouds interfered with the experiment, espe- 

 cially in £To. 8, when the light was considerably shaded by cloud. 



