APRIL 26, 1912] 
Friend has accomplished in a thoroughly 
satisfactory way in the present volume. 
The action of air and water and also steam 
upon iron is discussed at length, together with 
the various theories which have been advanced 
to explain corrosion. The author’s experi- 
ments to prove that a trace of carbonic acid, 
however minute, is essential in order that 
Tusting will take place, are of but academic 
interest, since such conditions can never be 
duplicated except with the refinements of a 
laboratory; and his conclusion that the elec- 
trolytic theory of iron is untenable is not 
warranted. In fact, the so-called acid theory 
which the author vigorously defends is none 
other than the electrolytic theory, where the 
assumption is made that the hydrogen ion con- 
centration in pure water is not great enough to 
produce a speed of reaction sufficiently high to 
make the rusting of iron at low temperatures 
obvious; while by the introduction of carbonic 
acid the concentration of the hydrogen ions 
is increased to such a point that iron will pass 
into solution rapidly enough to appear as rust. 
The book in many places suffers somewhat by 
the author’s unwillingness to make use of the 
conceptions introduced by the electrolytic 
theory which, were they used, would simplify 
the treatment. 
The chapters on the factors influencing the 
rate of corrosion exposed to natural forces, the 
action of acids and single salts and other elec- 
trolytes upon iron are most complete and give 
the reader a clear idea of the existing knowl- 
edge of this phase of the subject. Chapter 
XII. is devoted to the passive state of iron, 
and while it seems to contain all that we know 
upon the subject it emphasizes the fact that 
our present knowledge is far from giving us a 
satisfactory explanation for this peculiar phe- 
nomenon. The later chapters deal compre- 
hensively with the influence of chemical com- 
position upon the durability of iron, electrical 
and galvanic action, and the relative rate of 
corrosion of iron and steel. 
It is a matter of regret that the author has 
been misled, as have also the reviewer and 
others, by giving eredence to statements and 
data supplied by the American Rolling Mill 
SCIENCE 
661 
Co., of Middletown, Ohio, which he publishes 
on pages 114, 250, 276 and 251, regarding the 
purity of this firm’s products. For example, 
the material said to have the analysis pub- 
lished on page 114, as containing 99.954 per 
cent. iron, and which on page 276 is proposed 
as a standard for pure iron on which to base 
a corrosion factor, was later found by the au- 
thor himself, much to his surprise, to contain 
172 per cent. copper. 
The book constitutes a distinct and valu- 
able contribution to the literature on the sub- 
ject of corrosion, and will prove of interest to 
the general reader as well as of great service 
to those particularly interested in this field. 
Wittum H. Walker 
Principles of Electrical Engineering. By 
Harotp Prnper, Professor of Theoretical 
and Applied Electricity in the Massachu- 
setts Institute of Technology. New York, 
McGraw-Hill Book Company. 1911, Pp. 
xvili + 488. 
Convinced that the principles of electrical 
engineering are the principles of physics—a 
fact too frequently overlooked—and recog- 
nizing that a clear conception of these prin- 
ciples is essential for a proper understanding 
of the complicated reactions that take place 
in electric machinery and transmission cir- 
cuits, the author of this book in an admirable 
manner deals successively with the more im- 
portant phenomena of electricity and mag- 
netism, continuous and alternating currents. 
On the whole the treatment is satisfying and 
thorough. The mathematical discussions are 
adequate but, being merely a means to an 
end, are not too extensive. Descriptions of 
machinery and apparatus—even of the trans- 
former—are entirely omitted, the book having 
the same relation to electrical engineering as 
a first-class treatise on mechanics has to me- 
chanical engineering. There has long been 
a demand for a comprehensive and thorough 
treatise of this kind. It has been customary 
either to shirk the matter and use descriptive 
texts, or to use separate texts, on the elements 
of electricity and magnetism, electrostatics, 
alternating currents, ete. 
