146 Mr Whaiddington, Note on the Réntgen radiation. 
radiation is afforded by the observation that the velocity of the 
negative particles ejected from P is not very different from the 
velocity of those streaming out from the lime cathode*. This 
experiment was carried out as follows. An electrostatic volt- | 
meter connected between LZ and A gives the velocity (expressed | 
in volts) of the cathode particles shot out from Z. The potential | 
to which P charges up is a measure of the velocity of the 
particles ejected from P. In practice it was found necessary to 
keep the gold leaf in as sensitive a position as possible, and a 
convenient method of ensuring this was to keep the potential | 
difference between the electroscope plate and the leaf very nearly 
equal to V, the voltage giving instability. Thus the leaf was | 
charged to a positive potential v, and the plate was kept at such 
a potential p (positive or negative according as v was greater 
or less than V) as would satisfy the relation v-p=V. The 
voltage across the tube was then varied until the leaf did not 
drift from its zero position when insulated. We can then say 
that cathode particles of velocity not greater than v are being 
ejected from P. The following table gives a few of the results 
obtained in this way. 
} 
Velocity of lime cathode rays Velocity of particles from P 
(expressed in Volts) (expressed in Volts) 
128 100 
145 Aly 
187 152 
218 178 
velocity of lime cathode rays 
It is to be noticed that the ratio velocity of pantelesaieeiae 
is nearly constant*. 
_ * In this connection see Proc. Roy. Soc. A. Vol. uxxxvi. 1912. 
