Marcu 18, 1915] 
NATURE. 
63 

voted to applications involving only the use of 
the right-angled triangle; and identities occupy 
a subordinate position. The final chapter deals 
with complex quantities, Demoivre’s theorem, 
and applications to analysis. The last hundred 
pages of the book are taken up with logarithmic 
and other tables, calculated to five figures. The 
first-rate quality of the type employed deserves 
special mention. 

OUR BOOKSHELF. 
Experimental ‘Studies in Electricity and Magnet- 
ism. By F. E. Nipher. Pp. 73. (Philadelphia : 
P. Blakiston’s Son and Co., 1914.) Price 
125 dollars net. 
Turis book consists mainly of descriptions of the 
author’s experimental work, and summarises his 
reasons for accepting the one-fluid theory of elec- 
tricity. Photographs of discharges across a 
spark-gap, and traces on a photographic plate 
due to discharges over its surface, constitute the 
major part of the evidence. Much work has been 
done, and many interesting plates are reproduced, 
but it is doubtful whether the experiments are 
quite so conclusive as the author believes. 
Several novel ideas are introduced, such as the 
existence of conducting lines or “drainage 
channels” round the positive or “exhaust” elec- | 
trode in every kind of discharge, though it might 
be pointed out that this idea of a well-conducting 
channel is scarcely compatible with the consider- 
able potential-slope which exists in the positive 
column of a discharge tube. The suggestion that 
gravitational attraction is due solely to the “cor- 
puscular nebula” which permeates all matter is 
also novel; it is used to explain the explosive effect 
of discharging a Leyden jar through a wire. 
Loosely-worded expressions as “the corpuscular 
nebula is set into a rhythmical vibration” abound, 
and the phraseology generally is scarcely so precise 
as that usually found in scientific publications. It 
is possible that the case made out by the author 
suffers considerably from the manner in which it 
is presented, but certainly simpler explanations 
than those given would seem to suffice for some 
of the phenomena mentioned. The deflection of 
a magnetic needle due to a gust of wind might 
conceivably be due to a magnetic storm produced 
by the wind, but it would be advisable to see that 
the oscillation box is hermetically sealed or even 
evacuated, before accepting the magnetic storm 
hypothesis ! 
The Principles and Practice of Judging Live 
Stock. By Prof. C. W. Gay. Pp. xvili+413. 
(New York: The Macmillan Co.; London: 
Macmillan and Co., Ltd., 1914.) Price 6s. 6d. 
net. 
Tus volume is a very full compendium of all 
that belongs to a practice which has almost be- 
come a fetish in American agricultural colleges. 
To the student is given a card on which are 
printed the sections into which a horse, or some 
NO. 2368, VOL. 95] 

other animal, may be divided, and the marks to 
be awarded to each section. A draught horse, 
for instance, is divided into forty sections, and, 
as the marks total to 100, most sections get very 
small and none very large marks. The marks 
for some of the most important parts are these, 
given shortly: hocks, 6; hind cannons, 2; hind 
. . ae . 
fetlocks, 2; hind pasterns, 3; hind feet, 4; hind 
j legs, 4; walk, 6; trot, 4. 
Some of us who have tried it would have been 
exceedingly glad had this volume contained some 
evidence as to the educative value of the score 
card, because it may be doubted whether good 
judges are produced by its use; and because it 
fails to make sufficient distinction between the 
good and the supremely good, or the fair and the 
useless animal. All this, however, is rather a 
criticism of the system, or at any rate, of the 
scale of marks. 
If the system be admitted good and useful, 
Prof. Gay’s book is also good and useful. It 
contains good illustrations, descriptions of many 
breeds, an appendix containing the card marks 
for different breeds, and much information as to 
yields of milk, butter, beef, wool, and so on. 
Ie \ivie 
The Elements of Electro-Plating. By J. T. 
Sprague. Pp. vii+72. (London: E. F. N. 
Spon, Ltd., 1914). Price 1s. 6d.. net. 
Tue publication of this little volume brings home 
to us the sparseness of literature on the subject 
of electro-plating. Its publishers have con- 
sidered it worth while to re-publish, in this form, 
the intensely practical and well-written chapter 
dealing with the practice of the electro-deposition 
of metals which originally appeared in the late 
Mr. J. T. Sprague’s “Electricity: Its Theory, 
Sources, and Applications.” This classic was 
one of the best books of its kind when originally 
written, and the chapter on electro-plating was 
one of the best parts of the book. It is true that 
it is addressed ‘“‘rather to experimentalists, 
students, and general readers” than to those 
“mainly intent on business considerations,” and 
it is also true that as good electro-plating was 
done twenty-five years ago as now; yet one can- 
not but feel that the publishers would have done 
better to publish a new book than to re-publish 
an old one when dealing with a practical applica- 
tion of electricity. The reprint bears the new 
date 1914, and not the date of original publica- 
tion, but perhaps some of our older readers may 
be able to make a rough guess at the latter from 
the clue given by the following passage: “It 
is impossible to urge too strongly, alike upon the 
learner and the practical operator, the advantage 
of keeping in circuit a suitable galvanometer . . . 
and galvanometers to show current in amperes 
are now easily obtainable.’”” The book, old as it 
is, contains valuable directions and recipes, and 
if, instead of merely reprinting it, the publishers 
had employed a practical man of to-day to revise 
and re-write it, they would haye deserved our 
unstinted commendation. 
