328 
MR. W. CROOKES OK REPULSION RESULTING- EROM RADIATION 
Eig. 1. 
e 
consisting of a glass bnlb on the end of a tube, and having suspended in it, by means of 
a silk fibre, a horizontal glass stem with a disk of pith at each end. For a detailed 
description and the mode of exhaustion I refer to my last paper, the only point of difference 
being that in the present case one of the pith disks was coated with lampblack, the 
other remaining white. 
Before exhausting the apparatus I found that the white and the black disk were 
attracted about equally by the fingers, a bulb of warm water, or a hot glass rod. 
After exhausting it I tried the action again. The fingers repelled either disk 
strongly, and in about an equal degree ; and the same result was obtained with other 
sources of heat of low intensity. If the finger, a bulb of warm water, or a warm piece 
of glass or metal is held for some time close to the glass bulb, the two disks are repelled, 
and the rod connecting them sets equatorially, showing that the repulsion is equal on 
the black and the white surface. 
The bulb of water with enclosed thermometer (28) was raised to 100° C., and brought 
close to the bulb of the apparatus. The black and white disks were equally repelled, 
the connecting rod setting equatorially. 
A bath of fusible metal was prepared. In this a small copper ball was heated to 
different temperatures, and the action on the black and white disks noted. 
At 100° C. the repulsion of the two was equal. 
5 ? 55 
’5 55 
55 55 
the black was slightly more repelled than the white disk, the rod 
setting about five degrees from the equatorial position. 
150° 
200 ° 
250° 
300° 
