4 
DECEMBER 25, 1913] 
policy. Marine life is treated with the advantage 
of very recent researches ; but we doubt if irregular 
echinoderms are rightly styled “old-fashioned.” 
Is not the author thinking of the extinct but 
regular Paleozoic forms? The illustrations of 
carnivores from paintings by W. Walls are the 
finest in a most interesting book. Teachers of 
geography and lovers of animal life will alike 
rejoice in it. 
(5) Mr. Howarth has undertaken a hard task in 
giving a compressed picture of the commercial 
activity of the world. Such a work, however 
well done, cannot help reminding us of the lists 
of capes and rivers that once posed as lessons 
in geography. It is impossible to correlate all 
the details with the physical conditions of the 
country which they concern. The excellent descrip- 
tion of the industries of Sheffield (p. 95) shows 
what the author would give us in a more limited 
field or in a series of such volumes. Even among 
the mere statements of facts, such as “ Zinc is an 
important mineral product of Germany, Belgium, 
the United States, and elsewhere,” he hits upon 
something that makes us think; why, for instance, 
are precious stones “in great part products of hot 
countries ” ? GRENVILLE A. J. CoLe. 
TEXT-BOOKS OF PHYSICS. 
(1) Mechanics and Heat: an Elementary Course 
of Applied Physics. By J. Duncan. Pp. xiii+ 
381. (London: Macmillan and Co., Ltd., 1913.) 
Price 3s. 6d. . 
(2) Experimental Science. I., Physics. By S. E. 
Brown. Pp. viii+272. (Cambridge: University 
Press, 1913.) Price 3s. 6d. 
(3) Practical Physics-for Secondary Schools. By 
N. H. Black and Dr. H. N. Davis. Pp. ix +487. 
(New York: The Macmillan Co. ; London: Mac- 
millan and Co., Ltd., 1913.) Price 5s. 6d. net. 
(4) A Text-book of Physics. Edited by A. Wilmer 
Duff. Third edition revised. Pp. xvi+686. 
(London: J. and A. Churchill, 1913.) Price 
ros. 6d. net. 
(5) A Systematic Course of Practical Science for 
Secondary and other Schools. Book II., Ex- 
perimental Heat. By A. W. Mason. Pp. vii+ 
162. (London: Rivingtons, 1913.) Price 2s. 6d. 
net. 
(6) Paul Drudes Physik des Aethers auf Elektro- 
magnetischer Grundlage. Zweite Auflage. Neu 
bearbeitet von Dr. Walter Kénig. Pp. xvit+ 
671. (Stuttgart: F. Enke, 1912.) 
{) HE object of Mr. Duncan’s text-book, 
according to the preface, is to awaken 
interest in the applications of the principles of 
mechanics and heat to engineering and allied con- 
structive arts. The author has compiled a well- 
NO. 2304, VOL. 92] 
NATURE 
473 
arranged course of experimental work and de- 
scriptive matter in mechanics and heat, and, being 
an engineer, the applied side of the subject is kept 
well in the foreground. The first eleven chapters 
are devoted to mechanics, and contain, in addition 
to the more or less academic part of the subject, 
chapters on simple mechanism and hydraulic 
machines. The remaining ten chapters deal with 
heat, the action of the steam engine and the in- 
ternal combustion engine being presented in a 
very simple and lucid manner, and well illustrated 
by clear diagrams. It may be regretted that Mr. 
Duncan could not have included some of the 
more modern methods of thermometry in the 
section on temperature, the principles and con- 
struction of many of the instruments employed 
being quite intelligible to elementary students. 
The subject of thermal conductivity, too, is barely 
touched upon, and as lagging is of extreme im- 
portance to the engineer, the value of the book 
would have been considerably increased by the 
inclusion of a few well-chosen experiments on this 
subject. 
The book can be strongly recommended to first 
year students in technical institutes, and there is 
much in it that the average boy in the upper 
forms of a secondary school will appreciate. His 
interest in physics will certainly be stimulated by 
having the action of the cycle-motor and the 
motor-car engine so lucidly explained. Teachers 
of physics in schools may, however, object to the 
use of British units—Ib., ft., ° F.—and the physi- 
cist does not usually determine the latent heat 
of water by plunging a piece of ice weighing + lb. 
in 4 gall. of water. Objection may also be made 
to this constant being termed the latent heat of 
ice. An excellent feature of the book is the ques- 
tions and exercises appended to each chapter. 
(2) The volume on physics by S. E. Brown is 
the first part of a course on experimental science 
for use in secondary schools; part ii. is to deal 
with chemistry. The present book is divided into 
four sections, viz., (1) measurement, (2) hydro- 
statics, (3) mechanics, (4) heat. The author sup- 
poses a boy to spend from two to three years in 
working through the book, and this, in conjunc- 
tion with the chemistry course, should prepare 
him fully for such examinations as the experi- 
mental science of the Junior Locals or the Army 
Qualifying Examinations. As is now usual in 
books of this character, the manual may be used 
either in the laboratory or the class-room. The 
experiments are well selected, and great care has 
been taken in the preparation of the volume. We 
do not, however, like such statements as that on 
p- 3, where, in explaining how to use a scale for 
measuring lengths, we have the direction: ‘‘ Put 
