412 Radium and the Electron Theory. 
discover some action of the energy emitted by the new and 
wonderful manifestations on a current. Apart, however, 
from such a view of the working of the great physicist’s 
mind, can we not get a foothold in mounting to the heights 
of the electron theory by endeavouring to show that the 
X-rays, or the emanations from radium, do or do not have 
any discoverable action upon the passage of an electric 
current through aluminium for instance ¢ 
It must be premised that no mass is ascribed to the electron. 
Its supposable inertia is due to self-induction. On this con- 
ception it does not seem probable that particles shot off from 
radium, or ions resulting from the radiation of X-rays, could 
influence such immaterial bodies. | 
Nevertheless our view of the electron thecry might be 
influenced by proceeding to an actual test ; and looking at 
the results and limitations of poxsible experiments. ‘We 
therefore experimented as follows :— 
A metre of aluminium wire, No. 24, was wound in five 
turns around a thick sheet of lead, which was eight centi- 
metres in length and one centimetre in width. The wire was 
wound around the longest dimension of this shuttle-like piece 
of metal, and was insulated from it by thin sheets of vulcanite. 
The electric current, therefore, passed in one direction along 
the upper layer of ‘his wire, ell in the opposite direction 
slong the lower layer. The lead intervening between the 
upper and lower layer could serve to confine “the radiations 
from suitably placed radium either to the upper or the lower 
layer of wire. The lead shuttle with its layer of wire was 
enclosed in a lead cylinder, and a specimen of pure radiam 
bromide was enclosed at one end of the layers of wire so 
that its emanations could sweep along the upper or the 
lower layer of this wire. A lead diaphragm could be used to 
shut off the entire effects of the radium from the w ires. 
‘The wire was made one branch of a Carey-Foster 
bridge ; a suitable key enabled one to reverse the current 
through the aluminium wire, aud, after adjustment, the wire 
was exposed to the radiations from the aluminium under 
the varying conditions of reversals of current; radiations 
contined to the lower layer and afterwards to the upper 
Jayer. The bridge was competent to detect a change in 
resistance of one hundredth thousandth of an ohm. On 
account of the difficulty of distinguishing between a heating 
effect and what may be called an electrodynamic effect, the 
observations occupied a comparatively shor t interval of time. 
No instantaneous effect was observed ; a very slight creeping 
deviation of the gaivanometer- mirror came atter a con- 
siderable interval of time, which might have been due to 
