APRIL 7, 1923] 
NATURE 
459 

The final section is on general engineering economics 
and will be of great interest to commercial engineers. 
It is stated~that “ profits’ represent a return on the 
- capital over and above the normal rate of interest. 
For example, if the difference between income and 
expenditure was ro per cent. then assuming that 
6 per cent. is the normal rate of interest on invest- 
ments, the “ profit” would be 4 per cent. Apparently 
n America there is no agreed theory of depreciation, 
the straight-line or simple interest method and the 
-sinking-fund or compound interest method are both 
‘still used. 
The references given include the best American and 
English authorities and are useful ones. We can 
heartily recommend the book. A. R. 

























Our Bookshelf. 
The Yearbook of the Universities of the Empire, 1923. 
; Beeied by W. H. Dawson. (Published for the Uni- 
_versities Bureau of the British Empire.) Pp. xii+ 
‘ a2, (London: G. Bell and Sons, Ltd., 1923.) 
7s. 6d. net. 
THE latest edition of the Yearbook, revised and ampli- 
, should be of the greatest help not only to those 
officially concerned in university administration, but 
Uso to all who are interested in the developments 
Within the British Empire of higher and professional 
education. 
eover of an easily handled (and well indexed) volume 
the essential details of the calendars of the sixty-six 
universities of the Empire. Mr. Dawson, who has 
edited the book for the Universities Bureau, has accom- 
plished the task very creditably, and the abbreviations 
and other typographical devices to which he has had 
Tecourse do not in any way militate against intelligi- 
given is both accurate and adequate. 
The appendices, which now run to more than 150 
ages, contain some interesting information, not easily 
accessible elsewhere, regarding admission to the various 
professions and the qualifications necessary. A section 
on foreign universities gives some brief but useful 
articulars of the principal universities on the continent 
and also of the universities of the United States, includ- 
‘ing a list of the institutions approved by the Association 
of American Universities. 
Mention should also be made of the information 
relating to the admission to universities in the United 
‘Kingdom of persons educated abroad, to scholarships 
and grants for research, and to the distribution of 
subjects of study among British universities. Particu- 
larly interesting is a table showing the numbers of 
students from overseas, which suggests that the re- 
sources of this country for postgraduate and other study 
are now being appreciated. The total number of such 
students is more than 4ooo, At London University 
“alone there are 81 from Egypt, 336 from South Africa, 
46 from Canada, 72 from the United States, and 335 
from India. 
No, 2788, VoL. 111] 
It is no small feat to compress within the j 

The Microscopical Examination of Foods and Drugs. 
By Prof. H. G. Greenish. Third edition. Pp. xx+ 
386. (London: J.and A. Churchill, 1923.) 18s. net. 
Pror. GREENISH’s volume stands alone as a modern 
English text-book of the subject, and it is a matter of 
considerable satisfaction that author and publisher 
combine to keep the work abreast of the times. In the 
new edition, the text has been carefully revised and 
brought up-to-date, but we are informed that the 
inclusion of additional matter has not been possible on 
account of the prevailing high costs of paper and print- 
ing. We hope that by the time a further edition is 
called for, a means will have been found to overcome 
this difficulty, if it should still exist. 
The book is too well known to need detailed descrip- 
tion, but for the benefit of new students and others we 
may mention that its special value lies in the fact that 
it furnishes detailed information regarding methods of 
investigation which have been developed during many 
years by an acknowledged expert in the subject. In 
work of ‘this kind, prolonged and continuous experience 
is a sine qua non for accurate determinations, and the 
methods so fully and clearly set out in this handbook 
bear unmistakable evidence of such experience. The 
book is essential to all pharmacological laboratories 
and students, and we suggest that teachers of 
“ pure”? botany would find many hints as to methods 
and material which would be of assistance to them 
in obtaining fresh ideas for the scheme of practical work 
to accompany their histological lectures. If in a later 
edition it is decided to retain “ silk’ as a material for 
description, we suggest that space should be found for a 
somewhat fuller treatment of the subject, including a 
reference to the important results obtained by von 
Hohnel in his investigations of the different kinds of 
commercial silks. 
The Analysis of Non-Ferrous Alloys. By Fred Ibbotson 
and Leslie Aitchison. Second edition. Pp. ix+246. 
(London : Longmans, Green and Co., 1922.) 12s. 6d. 
net. 
THE fact that a second edition of this text-book has 
been called for is evidence that it has been found useful 
by analysts. War experience has led to an enlarge- 
ment of the field of non-ferrous alloys, and the authors 
have therefore added to the matter of the former 
edition an account of the analysis of alloys containing 
aluminium as their principal constituent, and also of 
those rich in nickel, such as cupro-nickel and nichrome. 
The light aluminium alloys form a particularly difficult 
class, and it has been found necessary to devote a 
special chapter to the separation of zinc and aluminium, 
the authors recommending the precipitation of zinc 
sulphide from alkaline solution or the electro-deposition 
of zinc. The otherwise excellent section on electrolytic 
analysis suggests that no cathodes other than platinum 
and mercury can be used successfully, but many 
laboratories now employ copper and nickel gauze 
cathodes with entire success ; an important considera- 
tion when the cost of platinum is so high. 
The subject of hydrogen sulphide precipitations is 
dealt with thoroughly, this being a matter on which 
it is most important to have a clear view of the con- 
ditions affecting ‘precipitation. The newer organic 
reagents, such as cupferron, are not described, 
