312 
Transactions of the Royal Society of South Africa. 
writer came to the conclusion that all the ionization produced in these 
substances when they were subjected to Ag X-rays, could be attributed to 
these corpuscles,* whilst the direct photographic evidence of C. T. E. Wilsonf 
amply justifies this conclusion. Sadler investigated the emission of a 
similar corpuscular radiation from metals, J one of his chief conclusions 
being that when the secondary rays are excited there is a special increase 
in the emission of corpuscular rays, whilst even if the secondary rays are 
not excited there is still a considerable amount of scattering taking place 
associated with the emission of corpuscles. Apparently then in solids as 
well as in gases the corpuscle is the a ^priori in the production of secondary 
rays, and consequently in the absorption of the primary rays. 
As an example of the atomic influence of X-rays we have the following. 
A mixture containing equal parts of SO2 and Hg absorbs X-rays to the same 
extent as a mixture containing equal parts of SHg and O^. The ionizations 
in these mixtures were shown by the writer to be different. The more recent 
work of Barkla and Philpot§ and of Moore || has really shifted the difl&culty 
into another quarter by their introducing a new constant, the Corpuscular 
Factor. 
In the work previously referred to, the writer began to make systematic 
investigations on the number of pairs of ions liberated in various gases 
during the passage of corpuscular rays through them. The conclusion 
adopted then was that the relative ionizations produced by either partial or 
complete absorption of their energy was equal to that produced by a similar 
absorption of X-ray energy. Barkla and Philpot showed that this conclu- 
sion needed but little modification, as will be seen from the values of h 
in Table I, which values are taken from this paper. The values of h are 
the relative numbers of pairs of ions produced in the gas for the complete 
absorption of a corpuscle liberated from gold leaf lining the inside of the 
ionization chamber. The relative numbers both and k were found to 
be independent of the wave length of the exciting X-rays. 
It is in the relative values of k that the only true molecular effects of 
X-rays on matter has yet been noticed. In order to account for the anoma- 
lous behaviour of SHg and SO2, viz. SH2 is ionized more, but absorbs 
less than SO2, the conclusion forced upon us was that there must have 
been some molecular effect in this case. The values of k show this con- 
clusively, and indicate too the seat of the molecular effect. The X-rays 
themselves act directly on the atoms irrespectively of neighbouring atoms, 
but in their passage through neighbouring molecules the high speed 
* Proc. Durham Phil. Soc, vol. v, Part 1, p. 43. 
t Proc. Roy. Soc. (A) 1912, Ixxxv, p. 285, 1911 ; Ixxxvii, p. 277, 1912. 
X Phil. Mag. (6) xix, p. 336. 
§ Phil. Mag. (9) xxvii, p. 187. 
II Proc. Roy. Soc. (A) 1915, xci, p. 337. 
