NOVEMBER 17, 1899.] 
mental laws of thermodynamics, giving the 
relations between temperature and entropy, 
the study of cycles, entropy computations, ap- 
plications to vapor and gas-engines, and closing 
with elaborate illustration in discussion of the 
results of a steam-engine trial. The discussion 
of the physics of steam by this method is par- 
ticularly complete and valuable and the tables 
appended will be found useful on many occa- 
sions. Within the sixty-six pages of text there 
are to be found abundance of suggestions and 
instruction and the whole is written in a thor- 
oughly scientific and systematic manner, with- 
out waste of words or loss of energy in diffuse 
explanation. 
It should be noted by the readers of these 
little treatises that, occasionally, in the dia- 
grams, an error will be noted in the assignment 
of a quantity of entropy to a mixture of steam 
and water less than that of water alone. 
The interested reader of this collection of 
brochures should complete his work, if not 
already familiar with them, by examining the 
added list of papers. Professor Gibbs, as the 
real pioneer in the use of this interesting 
method, Linde as the first to apply it to the re- 
frigerating machine, Gray as the writer whose 
enthusiastic and painstaking elaboration of the 
system first brought it to the attention of en- 
gineers in such a manner as to insure its care- 
ful examination and later general use, Wil- 
Jans, the pioneer in its application as a regular 
process of reduction of observational data to 
form for deduction, and Sankey, his co-laborer, 
also, are entitled to distinction only less than 
that accorded to the founders of the science 
which this system illustrates. Professor Dur- 
and, illustrating talent as an instructor as well 
as familiarity with the state of the art to date, 
presents the most complete and intelligible ex- 
position of the theory of the entropies—for he 
shows that there may be an indefinite number 
—and, availing himself of suggestions by An- 
cona in a very notable paper in the Zeitschrift 
of the German Society of Civil Engineers for 
1897, produces diagrams which ‘are read with 
great ease and interpreted as readily. This is 
a luminous and clear as well as concise exposi- 
tion of the subject. 
R. H. THURSTON. 
SCIENCE. 73 
Alternating Currents of Electricity and the Theory- 
of Transformers. By ALFRED STILL. Whit- 
taker & Co. 8vo. 1898. 179 pages. 
Alternate Currents in Practice. Translated from 
the French of Loppé and Bouquet by F. J. 
Morretr. Whittaker & Co. 8vo. 1898. 
372 pages. 
In the application of science to engineering 
the scientific principles involved have usually 
been very fully developed beforehand by the 
student of pure science. In the engineering 
applications of alternating currents, however, 
our educational and scientific men have been 
behindhand. The fundamental mathematical 
principles of alternating currents have indeed 
been developed mainly by men outside of the 
engineering profession, as exemplified by the 
epoch-making book of Bedell and Crehore, but 
the theory of actual engineering apparatus, 
such as the transformer, the rotary converter, 
the induction motor, ete., has been developed 
mainly by the engineer, and during the past few 
years our electrical engineering instructors have 
been looking eagerly to the manufacturing elec- 
trica] engineer, not only for the details of design 
and construction, but also for the full and com- 
plete theory of their machinery as well. The 
engineer who has contributed most in this line- 
is perhaps C. P. Steinmetz. 
The electrical engineering instructor has now 
access to literature containing very complete 
developments of fundamental principles and 
very complete theoretical analysis of actual 
engineering machinery, and the problem which 
confronts him is to adapt this wealth to the re- 
quirements of instruction. 
Instruction in electrical engineering should 
consist of two parts, as it seems to us, namely, 
an elementary part in which the general prin- 
ciples of the various branches of the subject 
are systematically developed, and a more prac- 
tical part devoted to the design, construction 
and operation of machines, appliances and in- 
stallations. In some branches of electrical 
engineering, indeed, the elementary part is 
little more than a course in theoretical elec- 
tricity, but in alternating currents a great 
variety of principles arise which are not prop- 
erly included in any general course in electrical 
theory, and it seems proper for the student to~- 
