2 NATURE 
The difficulty of two elements having an 
identical spectrum is considerable; it is suggested 
that inasmuch as the spectra are characteristic of 
the movement of the electrons in an element, 
rather than of its mass, two elements in which 
the electrons will have identical motions must 
have the same spectrum. Mr. Aston’s researches 
on two “neons,” which can be separated from 
each other by diffusion, but which show no differ- 
ence in spectrum, are adduced as proof of this 
point of view. It will be remembered that it was 
owing to Sir J. J. Thomson’s finding that ordinary 
neon contains a small proportion of an element 
of atomic weight 22, which led to Mr. Aston’s 
research. Here, again, one can only wonder that 
two elements, neon I. and neon II., of different 
atomic weights, 20 and 22, which can be separated 
by diffusion, according to Mr. Aston, have 
identical vapour-pressures, for they cannot be 
separated by fractional distillation. 
Mr. Soddy has invented a modification of the 
periodic table which represents his new arrange- 
ments; it is three-dimensional. 
Much of the book under review is taken up with 
detailed discussion of the generalisation of which 
a brief account has been given. The concluding 
section on the ‘“‘ Nature of the Argon Gases,” puts 
forward the view that these elements are inactive 
owing to their great affinity for their valency 
electrons. Whereas an atom of sodium, in com- 
bining with an atom of chlorine, loses an electron 
to the chlorine, itself becoming an ion, an atom 
of argon has no such tendency, being very firmly 
bound to its electron. 
This work of Mr. Soddy’s must be termed 
“provisional”; it brings before the reader the 
state of knowledge regarding the sequence of 
radio-active elements, but it does more; it 
elaborates a hypothesis capable of correlating 
these facts; a very ingenious theory which, how- 
ever, its author would be the first to acknowledge 
is still in need of support. WR: 
TECHNICAL MYCOLOGY. 
(1) Einfiihrung in die Mykologie der Gebrauchs- 
und Abwdsser. By Dr. A. Kossowicz. Pp. vii 
+222. (Berlin: Gebriider Borntraeger, 1913.) 
Price 6.60 marks. 
(2) Die Gérungsgewerbe und ihre naturwissen- 
schaftlichen Grundlagen. By Prof. W. Henne- 
berg and Dr. G. Bode. Pp. v+128. (Leipzig: 
Quelle und Meyer, 1913.)) Price 1.25 marks. 
(1) R. KOSSOWICZ surveys the subjects 
of water and sewage purification from 
the bacteriological point of view. To a large 
extent the book summarises researches that have 
NO.=2214= “VOL. 93) 
[Marcu 5, 1914 
been carried out on these subjects, though, on 
account of their number, the summary of each 
research is necessarily very brief. Its chief value 
consists in the contained bibliography—every page 
teeming with references to the literature—and the 
student, engineer, or hygienist desiring a guide 
for his practice will be bewildered by the mass of 
detail. Diagrams and figures of filters and filter- 
beds, sterilising apparatus, sedimentation tanks 
and plant for the biological treatment of sewage 
have been freely introducéd, and form a useful 
feature. 
The earlier chapters deal with the bacterial 
content of waters and the factors which modify 
it, the occurrence of pathogenic microbes in water, 
and the self-purification of water, and in sub- 
sequent chapters the subjects of sand-filters, 
chemical and other methods for the purification 
and sterilisation of water, sewage farms, the bio- 
logical treatment of sewage, and the purification 
of trade effluents are considered. 
(2) This little book gives a brief and simple, 
though at the same time excellent, survey of 
fermentations and the fermentation industries. 
The yeasts, bacteria, and moulds concerned in 
fermentations—alcoholic, souring of milk, acetic 
and butyric acids, etc.—are first described, with 
an account of their structure, development, and 
occurrence. The chemical composition of the 
substances fermented, the nature of the chemical 
changes involved, enzymes and enzyme action are 
next considered, and finally a description is given 
of the industrial processes involved in the pro- 
duction of beer, wine, and spirits, pressed (Ger- 
man) yeast, bread and vinegar, soured milk and 
“sauerkraut,” cocoa and coffee. The text is illus- 
trated with a number of figures of the micro- 
organisms involved and of the industrial plants 
employed in the fermentation industries. 
R., T. HEWLETT: 
HUMAN MATHEMATICS. 
(1) A First Book of Practical Mathematics. By 
T.. S...Usherwood ang:C. J.-A.) Trimble em 
iv+182. (London: Macmillan and Co., Ltd., 
TOlgs)) «Price 1s." 6d. 
(2) Practical Geometry and Graphics for Advanced 
Students. By Prof. Joseph Harrison and G. A. 
Baxandall. Enlarged Edition. Pp. xiv+677. 
(London: Macmillan and Co., Ltd., 1973.) 
Price 6s. 
(3) Practical Mathematics. By Norman W. 
M’Lachlan. Pp. viii+184. (London: Long- 
Price 2s. 6d. net. 
Enonces et Solu- 
Avec une Preface 
mans, Green and Co., 1913.) 
(4) Exercices d’Arithmétique. 
tions. By J. Fitz-Patrick. 
5 
we 
* 
if 
ef 
