596 
of cleanliness and organisation. Unfortunately, the 
difficulties of distribution are such that the consumer 
cannot with certainty buy his pound of margarine in 
perfect condition unless his retailer is certain of a quick 
sale ; and although the same difficulty applies to butter, 
more tolerance is extended to the older commodity. 
A problem which is engaging an increasing amount 
of attention in the fat industry is that of texture. A 
fat, that is to say, a triglyceride, may either contain 
three of the same acid radicles or two or more different 
acid radicles, in which case it is spoken of as a mixed 
glyceride. A mixed glyceride has properties very 
different in regard to melting-point, consistency, etc., 
from a mixture of glycerides. Again, fats which, 
when separate, have similar properties which are 
satisfactory from the technical point of view, may 
have altogether different and far less satisfactory 
properties when mixed. Such theoretical considera- 
tions have an important practical bearing in the 
chocolate and biscuit industries. 
Sufficient has perhaps been said to indicate how 
diverse are the problems to be found within the in- 
dustries of the fats and oils, and how wide must be the 
scope of a work dealing with their chemical technology. 
Dr. Lewkowitsch’s book has played no small part in 
aiding many an investigator to do his share in advancing 
the knowledge of them, and each new edition has 
reflected in turn the new information acquired. The 
newest edition is no exception to this and is replete 
with information, and it is with no wish to detract 
from its value that it is suggested that when the 
time comes for it again to be revised it may be 
advisable largely to remodel the plan on which it 
is built. ELBA. 

Our Bookshelf. 
(1) Steam Turbines. By Prof. W. J. Goudie. Second 
edition, rewritten and enlarged. Pp. xvili+8oq. 
(London : Longmans, Green and Co., 1922.) 30s. 
net. 
(2) Modern Practice in Heat Engines. By T. Petrie. 
Pp. xi+264. (London: Longmans, Green and Co., 
1922.) 15s. net. 
(3) Notes and Examples on the Theory of Heat and Heat 
Engines. By John Case. Second edition, revised 
a enlarged. Pp. vit138. (First issued in 1913 
“A Synopsis of the Elementary Theory of Heat 
ahd Heat Engines. ”) (Cambridge: W. Heffer and 
Sons, Ltd. London : Simpkin, Marshall and Co., 
Ltd. ean 75. 6d. net. 
(1) Pror. Goupin’s treatise was first issued in 1917, 
and the volume has become a standard work. Its 
value has been proved by teachers, students, and 
professional men engaged in practice. The book 
has been out of print for some time, owing to the 
author’s desire to bring it up-to- date, and this has 
NO. 2792, VOL. III] 
NATURE 

[May 5, 1923 
meant the formidable task of rewriting practically 
the whole work. To those acquainted with the first 
edition, the result will be found extremely serviceable, 
inasmuch as not only recent designs are included, but 
also additional matter is given bringing the theory up- 
to-date. The thoroughness with which the task of 
revision has been carried out is evidenced even in the 
numerical examples. The volume is now one which 
cannot be dispensed with by any one engaged in steam 
engineering. : 
(2) This book is divided mto three sections dealing 
with steam boilers, steam prime movers (including 
steam turbines), and internal-combustion engines re- 
spectively. Some of the descriptive parts of the section 
on steam turbines are taken from the article written 
by Prof. Gerald Stoney and the author for the “ Dic- 
tionary of Applied Physics’ (Macmillan). The field 
covered is wide, and the book contains a large number 
of illustrations descriptive of the details of modern 
plants. Despite this, the author has succeeded in 
presenting as much of the theory as the average 
student requires in his college course. Students re- 
quire a general treatment such as is contained in the 
present work, and they will also appreciate the fact 
that it contains no very difficult mathematics. There 
are a number of worked examples in the text, but it 
would be an improvement if some exercises were in- 
cluded for the purpose of enabling the student to test 
his knowledge. 
(3) Mr. Case’s volume of notes, worked examples, 
and exercises on the theory of heat engines will be 
helpful to many students. Most parts of the subject 
are covered, and those omitted do not present any 
particular difficulties. 
The Pageant of Nature: British Wild Life and its 
Wonders. Edited by Dr. P. Chalmers Mitchell. 
(Complete in about 36 fortnightly parts.) Part 1. 
Pp. 72. Part 2. Pp. 73-144. Part 3. Pp. 145= 
216. (London: Cassell and Co., Ltd., 1923.) 1s. 3d. 
net each part. 
THE avowed object of this new publication is to provide 
the libretto to the play of Nature in Britain, and, by 
describing in clear and accurate language the varied — 
phenomena which can be observed at all seasons of the 
year during almost any country ramble, to stimulate 
observation, to foster a love of Nature and, perhaps, to 
spur on to further independent discovery the keener and 
more gifted of its readers. It is essentially a book of 
Nature study, of observation in the field, of animals and _ 
All the authors — * | 
plants in their natural surroundings. 
who have contributed to its pages—and there are no 
fewer than twenty in the three parts under notice—are 
well known for their admirable first-hand studies of wild — 
Nature, in one or other of its many branches, with eye, - 
field-glass, and camera and, may we add, with pen, and 
their articles are illustrated with original photographs 
taken either by themselves or by other equally skilled 
and enthusiastic Nature photographers. 
It is perhaps invidious to make a selection from a 
number of articles all of which reach a high level of 
charm, accuracy, and simplicity ; but special mention — 
should be made of Dr. Francis Ward’s delightful 
studies of otters and fishes, illustrated by a unique 
series of remarkable photographs of these animals taken ~ 
en On 
