546 
MR. W. CROOKES ON REPULSION RESULTING FROM RADIATION. 
121. The following experiment was suggested by Mr. Cromwell F. Varley, F.R.S., 
who informs me that he considers the results conclusive against the electrical theory. 
A torsion-apparatus was prepared, as 
shown in fig. 11. The inside of the 
tube ( a b) is lined with a cylinder 
of copper gauze, having holes cut in 
the centre ( c ) for the passage of the 
supporting- thread ( d c) and the index 
ray of light, and holes at each end 
to admit of the plates (e,f) being 
experimented with. A hole drilled 
in the plate (b) allows a wire to pass 
from the copper gauze to the out- 
side, so as to give me electrical access 
to the gauze lining. Under the 
most diverse electrical conditions, 
whether insulated or connected with 
“ earth,” this apparatus behaves nor- 
mally when heated; neither can I detect any electricity when the plate e or^is under 
the influence of radiation if I connect the wire g with a delicate electroscope. In 
experimenting with this apparatus I have also completely immersed it in liquids, such 
as water, solutions of metallic salts, ether, disulphide of carbon, &c. The heat has 
been applied in these cases by introducing a glass bulb containing water at different 
temperatures and a thermometer (28). Under all these varied circumstances the 
movements took place in the regular manner, and no electrical action whatever could 
be detected. 
122. I have already discussed Professor Osborne Reynolds’s theory of evaporation 
and condensation somewhat fully in the already quoted Physical Society paper *. I 
will, however, describe the following experiments, which I think prove that Professor 
Reynolds has not suggested a theory which accounts for all the facts of the case, and 
therefore has not hit upon the true explanation. 
A thick and strong bulb was blown at the end of a piece of very difficultly fusible 
green glass, specially made for steam-boiler gauges. In it was supported a thin bar of 
aluminium at the end of a long platinum wire. The upper end of the wire was passed 
through the top of the tube and well sealed in, for electrical purposes (120). The 
apparatus was sealed by fusion to the Sprengel pump, and exhaustion was kept going 
on for two days, until an induction-spark refused to pass across the vacuum. During 
this time the bulb and its contents were several times raised to a dull red heat. At 
the end of two days’ exhaustion the tube was found to behave in the same manner 
* Loo. cit. ; also Chemical News, July 17, 1874. 
Eig. 11. 
