ELECTRICAL PROPERTIES. OF PURIFIED SULPHUR. 249 
soluble quadrants and repelled from the insoluble, the needle 
being charged positively. 
The second set of quadrants was then made, and the same 
series of experiments was gone through. The quadrants were 
diselectrified as usual and placed in position. Exactly the same 
results were obtained as with the first set after diselectrification. 
The electrophorus was first used for charging. There was. a 
large deflection towards the soluble quadrants. On rotating 
through 90° the deflection was reversed, still towards the soluble 
quadrants. The rotation was performed repeatedly without any 
contradictory result being obtained. The insulation of the case 
and brass quadrants was altered without alteration of the result. 
The battery being used to charge the needle a positive charge 
gave a deflection in the same direction as before ; a negative 
charge turned the needle towards the insoluble quadrants. 
One of the insoluble quadrants was rubbed a little with a bit 
of flannel, and the deflection on charging with the electrophorus 
was reversed, turnirg towards the insoluble quadrants, and show- 
ing that sufficient negative electricity is easily developed on the 
insoluble sulphur, to overcome that on the soluble, due to contact 
effect. This reversal of effect ceased after about fifteen minutes. 
At one time, with these quadrants, we noticed a reversal of 
the direction of deflection upon greatly increasing the charge ; but 
this was much better seen, and further studied, with the third set 
of quadrants. 
The third set of quadrants was made in the same dish that was 
used for the second, but greater care was taken in their manu- 
facture. Instead of roll sulphur pure Chance Claus sulphur once 
distilled was used. Much greater care was taken to ensure 
perfect solubility in the soluble quadrants. The sulphur used for 
them was very gradually heated to about 116° C. in an oil-bath, 
several hours being consumed in the process. The sulphur was. 
left for some time at this temperature, and then slowly cooled. 
This process was repeated a second time. In order to melt it, it 
was heated in the oil-bath again to 128° C., and then poured into 
the zine dish. In order to obtain a smooth even surface, and to 
distribute the sulphur over the quadrants, the surface had to be 
smoothed by a piece of aluminium heated till particles of sulphur 
would just melt on it. 
Besides the diselectrification as before, this set was diselectrified 
in-situ by means of a fine gas jet. In order to prevent the 
possible electrifying effect of rubbing when rotating the zinc dish 
upon some other substance, a zine plate, cut from the same piece 
as that from which the dish was made, was placed beneath it, and 
to vary the tests of reversibility, two mirrors, at right angles, 
were fixed on to the needle-rod, so that the needle could be 
rotated as well as the quadrants and its deflections observed. 
