666 Prof. Bragg and Dr. Madsen : An Experimental 
in all the cases we have tried the want of symmetry is obvious. 
In fig. 3 are shown the details of one other case, in which 
n — 
■C Ic+h(B) 
(1) Current with plates arranged as above .... 59*8 
(2) „ „ A and B inverted 54*4 
(8) As in (1), but base PQ changed to carbon . 505 
carbon and lead were the materials used, and the form of 
the chamber was different. It seems unnecessary to give 
more, because in the first place the experiments are easy to 
repeat : and in the second place, the complete quantitative 
analysis of the figures depends on several factors, the in- 
fluence of which is imperfectly understood, such as the 
previous screening of the rays, the form of the chamber, and 
the respective parts played by the original 7 rays, cathode 
rays, and secondary 7 rays if any such exist. The experi- 
ments as they stand show how far away is that symmetry 
which the aether-pulse theory demands. It seems to us that 
there is no escape from the conclusion that the y rays are 
not aether pulses. 
Let us therefore proceed to consider the hypothesis that 
the 7 rays are material. In the paper already mentioned it 
was argued that they might well consist of neutral pairs, 
liable to be broken up on encountering atoms or parts of 
atoms ; and that the secondary cathode radiations might be 
the negative particles thus set free. Let us suppose, pro- 
visionally, that the particles when set free move at first in 
the direction of the 7 stream, but are subsequently scattered 
in the usual manner of /3 rays. [It is here that the absence 
