59° 
NATURE 
[JANUARY 15, 1914 
groupings of two and of three carbon atoms; the 
last are produced only when the vapours of com- 
plex carbon compounds are induced to form 
“positive rays.” 
The question of multiple charges carried by an 
atom is discussed at considerable length; it would 
appear that a mercury atom may carry as many 
as 8 charges; an atom of krypton, 4 or 5; one of 
argon, 3; one of neon, 2; of nitrogen and of 
oxygen, 2; and of helium, also 2; no hydrogen 
atom with more than one charge has been ob- 
served, The larger the number of charges carried, 
the fainter the line. But the intensity of the para- 
bolic line, whether seen on a Willemite screen or 
photographed, is by no means proportional to the 
amount of element producing it. The hydrogen 
parabola, for instance, is always much more 
intense than would be accounted for by the relative 
amount of hydrogen present. To prove this, a 
most ingenious device was adopted; a parabolic 
slit in the screen was interposed between the 
source of the rays and a metallic box, connected 
with an electrometer; by altering the intensity of 
the magnetic field, the parabolas were made ta 
fall on the slit, and the rays passed through into 
the box, and registered their intensity on the 
electrometer. In this way the relative quantity 
of the gaseous elements present was estimated 
with fair accuracy. 
Proof was also obtained that helium is a mon- 
atomic gas, while oxygen and hydrogen are 
diatomic; for in the discharge-tube, besides de- 
tachment of a corpuscle from a molecule, the split- 
ting up of a molecule into its constituent atoms 
takes place. 
Chapters foilow on retrograde and on anode 
rays; and Stark’s interesting observations on the 
Doppler effect are described and amplified; also a 
short account of the spectra produced by bom- 
bardment with positive rays. 
Next follows a chapter on the use of positive 
rays for chemical analysis; the preface states that 
“one of the main reasons for writing this book 
was the hope that it might induce others, and 
especially chemists, to try this method of ana- 
lysis.”’ I fear that it will not have this result. It 
is a pity that Sir Joseph Thomson in this chapter 
had not given a more detailed account of his 
methods, with more elaborate diagrams of the | 
apparatus. Even to one skilled in work of this 
nature, what appear no doubt commonplaces to 
him require elucidation. I‘or example, how many 
amperes-are necessary to incite his magnets? 
What is the size of the magnets? What electric 
field is required? What voltage must be applied 
to the plates giving an electrostatic field? One 
would require to visit the Cavendish laboratory, 
NO. 2207. VoL.-a2] 
or to trouble its director with correspondence 
before one could set up an apparatus in working 
order. 
A discussion then follows of Mr. Aston’s in- 
teresting investigation of neon, with the object of 
ascertaining whether neon, which has the atomic 
weight 20°2, contains a gas of atomic weight 22; 
the existence of the latter is indicated by positive 
rays in neon. To my mind it is scarcely credible 
that a mixture of gases, separable by diffusion, as 
Mr. Aston finds, cannot be separated by distilla- 
tion and yet neither Mr. Watson, who determined 
the atomic weight of neon, nor Mr. Aston, who 
repeated Mr. Watson’s experiments, have been 
able to effect any separation by fractionation. 
Further work, however, will no doubt settle the 
question. The existence of “X,” is next treated 
of; and the reasons for believing it to be a hydro- 
gen ‘‘ozone”’ appear to be cogent. 
Finally, Sir Joseph Thomson deals with the 
continuous production of helium when certain sub- 
stances are bombarded with kathode rays. Again, 
he does not inform us what gas was present. He is 
rightly very cautious in drawing any definite con- 
clusions from his experiments; but at present his 
bias is in favour of the possibility of disintegra- 
tion; that the matter bombarded disintegrates into 
helium, and some other “elementary” form of 
matter. He says:—‘‘The view that helium can 
be got from other chemical elements raises ques- 
tions of such a fundamental character that few 
will be prepared to accept it until every other 
explanation has been found to be untenable.” The — 
production of helium from radium, from niton, 
from thorium, and from actinium is now accepted — 
as an undoubted fact; questions of “a funda-— 
mental character ” have been raised and answered ; 
and it appears to me to need a very small stretch — 
of imagination to suppose that while some 
“elements” spontaneously undergo exothermic 
changes with evolution of helium, others require 
external sources of energy before disruption takes 
place. W. R. 
GEOLOGY AND MINERALOGY. 
(1) The Earth: Its Genesis and Evolution con- 
sidered in the Light of the most recent Scientific 
Research. By A. T. Swaine. Pp. xix+277+ 
xi plates. (London: C. Griffin and Co., Ltd., 
1913.) Price 7s. 6d. net. 
(2) Grundziige der geologischen Formations- und 
Gebirgskunde. By Prof. A. Tornquist. Pp. iv 
+296. (Berlin: Gebriider Borntraeger, 1913.) 
Price 6.80 marks. 
(3) Determinative Mineralogy. With Tables for the 
Determination of Minerals by means of their 
Chemical and Physical Characters. By Prof. 
