as 15°. This deflection was so small as not materially to 
diminish the projection of the surface exposed to the light, but 
it was found practically to destroy the repulsion. Four experi- 
ments were made, each consisting of four readings of the zero 
point, and as many of the position of the dise after exposure, 
the observer removing each time to a distance from the appara- 
tus; the results are given belo 
Toward the light. Away from light. 
0°-2 2°*4, 0 
This gives as the mean result a repulsion of 0°°8, and shows 
_ that the phenomenon differs essentially from that involved in 
a Crookes’ radiometer. 
With this same apparatus, the disc being still bent out of Mi 
vertical position, I now repeated the fandamental ae 
of exposing the apparatus to the action of a naked gas ia 
under atmospheric pressure ; the results of these trials are giv 
below. ved 
(1.) The disc remained stationary a moment, and then mo 
toward the light. 
2.) Same result. : 
‘3 Moved a few degrees away from the light, afterward 
40° or 50° toward it. srees 
(4.) 8° away from light, then a large number of 
toward it. ya from 
(5.) Small deviation toward light, small deviation away 
it, large deviation toward it. ‘ht. 
(6.) Dise stationary, 5° away, 50° or 60° toward lig aa 
i “.) 5° or 6° toward light, stationary, large deviation 
ight. i- 
The blackened disc was now arranged so as to ba nie 
cally, and the experiment repeated, all the other ¢o 
remaining unaltered. rd flame; 
(1.) Repelled 20°; then began to move slowly towa in same 
on extinguishing the latter, a large sudden motion 
ction. 
dire 
