exxx Proceedings of the Asiatic Society of Bengal. {N.S:, XV, 
to observe this remarkable phenomenon again, and although 
the conditions were reproduced apparently in every particular, 
it was never again observed. Although this incident has no 
radioactive processes, vs — difficulty of reproducing the full 
eee or of an experim 
regard to this nec experiments we have bee 
pects there has been no question of faulty observatiba? 
h 
the main or only product, the source can hardly have been at- 
mospheric, for the light inactive gases from air show a strong 
neon spectrum in which the helium is visible with difficulty. 
Yet in many cases, notably in the cathode ray bombardment 
of heavy metals and salts of caesium, rubidium, and potassium 
by Collie, and in some of the jacketed tube experiments o 
Collie and of Bhiteresi’ helium was the main product. In 
spite of the criticism of Soddy, it is extremely unlikely that, 
powder used by Collie in connection with Merton’s nd 
could have furnished helium in the quantities observed had it 
been produced by the natural radioactivity of the metal. 
has been observed, the helium must have been present in con- 
siderable quantity, for comparatively large amounts of helium 
may be present in neon without the spectrum of the former 
being visible. 
The possibility of the pre-existence of helium or neon in 
the materials used has constantly been kept in mind, and no 
trace of either of these gases has been detected when the 
hydrogen and oxygen used in the experiments were examined, 
nor when the glass was fused in a vacuum, and the metal elec- 
trodes fused or dissolved. 
have purposely refrained, in this brief survey, from 
attem mpting an any explanation of the results described, ‘becau use 
fu only in so far as it suggests further experimental work, in 
which case it may well be left to those 
