JuLy 21, 1912] 
NATURE 
473 
are also some features in English and Continental 
practice which are worthy of study and should 
therefore not be omitted in a handbook on the 
subject. Thus the Merz-Price safety device, which 
has made the linking-up of the power-stations on * 
the north-east coast possible, and is now also 
extensively used on the Continent, is not even men- 
tioned, the subject of graded cables is dismissed 
with a few lines, there is no mention of Nagel’s 
condenser bushings, and the hexagonal arrange- 
ment of duplicated power lines, now almost uni- 
versal in Switzerland, is also ignored. 
Another rather serious omission is that of the 
Thury D.C. system of transmission. This has 
been in successful operation on the Continent for 
many years at voltages exceeding 100,000, and it 
has quite recently been taken up by Mr. Highfield 
in England. Some of the information as to con- 
ductors might have been given in a more scientific 
way. Thus the “breaking weight” for hard and 
annealed copper wire is given in pounds with re- 
ference to the B and S gauge. It is also to be re- 
gretted that the author has not emancipated him- 
self from the unit called the “circular mil.” There 
is no difficulty in expressing the area of a wire 
in square inches, or square mils if a smaller unit is 
desired, but to use the C.M. is unscientific and 
confusing. 
The constants of a transmission line are treated 
in a clear manner, and the transition from the 
single to the polyphase circuit is made in an 
easy and natural way, the mathematics employed 
being throughout of an elementary kind and easy 
to follow. Unfortunately the author lets his 
vectors rotate clockwise, which must be a little 
irksome to those readers who have, in conformity 
with the decision of the Turin Congress, ac- 
customed themselves to think of vectors revolving 
counter-clockwise. 
In “Direct and Alternating Current Manual ”’ 
we have a second and improved edition of a book 
which appeared three years ago under the title, 
“Direct and Alternating Current Testing.” Al- 
though the book is primarily concerned with the 
testing of machinery, it does not simply give in- 
struction how such tests should be made, but it 
also gives digests of the theory of the machines 
themselves. The only exception to this is the 
chapter on wave analysis, where Runge’s method 
for eighteen known ordinates is given without 
proof. The instruction is, however, so clear and 
exemplified by a numerical example that the reader 
cannot fail to apply the method correctly. 
Two chapters only are devoted to D.C. machine 
tests. There we find some of the well-known 
methods described, but the statement on page 46 
that in a shunt motor the iron losses are independ- 
NO. 2228, voi. 89] 
Q n 
ent of the load will scarce be confirmed by engin- 
eers who have made such tests carefully. Chapter 
iii. treats of alternators, and especially of the 
relation between excitation and terminal voltage. 
We are told about the “optimistic” and “pessi- 
mistic’’ methods of determining drop, but these 
favourite expressions of American writers do not 
carry us very far in separating the two causes, 
namely, inductance and armature ampere turns, 
which combined produce the drop. This chapter 
is rather disappointing. It is also somewhat tire- 
some that throughout the book the authors use 
copious foot-notes, sometimes in correction of a 
statement made in the text. The general proper- 
ties of alternating current circuits and transformer 
tests are treated in Chapters iv. and v., but the 
treatment is rather elementary and does not include 
some important tests, such, for instance, as heat- 
ing and efficiency of large transformers. We are 
merely told on page 177 that a heat run is “usually 
made by some kind of opposition or pumping back 
method, of which there are several.’’ Then follows 
a general description of one such method, but as 
no diagram of connections is given, the few lines 
of text will not be of much use to the student. 
The following chapters, dealing with polyphase 
currents, are more satisfactory, especially the 
analysis of the effect of upper harmonics in star 
and mesh three-phase systems and power and 
power factor measurements. Next follow chapters 
on the induction motor and the circle diagram, 
frequency changers, synchronous motors, but the 
single-phase commutator motor is not discussed. 
“Storage Batteries” is an unpretentious, but 
very attractively written little volume. In dis- 
cussing the general principles of chemical storage 
of energy the author starts from Faraday’s laws 
of electrolysis and takes the reader by easy stages 
to the predetermination of the E.M.F. of any com- 
bination, to the ionic theory, the cell-reaction, and 
finally to the theory of the reversible lead accumu- 
lator. When dealing with the relation between 
discharge rate and capacity, the author makes 
use of Peukert’s formula I”t=constant (though 
without acknowledgment), and gives a very instruc- 
tive series of curves, showing how the exponent 
varies in different types of cells. Examples are 
also given of some commercial types of cells, and 
amongst these it is interesting to find the Edison 
cell, about which so much has been written and 
so little is known. 
The last book on the above list is an exhaustive 
treatise on apparatus and machinery concerned 
with heavy electrical engineering. The book will 
be found useful not only by students, but even 
more so by men in practical work. The author 
is not content to give the theory of machines, 
