566 
Notices of Boohs. 
[October, 
lent to saying that about 13 per cent of the whole heat expended 
may be turned into mechanical work, or about 50 per cent of the 
heat which would be turned into work in a theoretically perfect 
engine working between the same limits of temperature.” The 
average result, however, even in economically worked engines, 
is much less, 
We have now, it is hoped, given sufficient particulars of the 
contents of this book to show its great value as a work calculated 
to lead the thinking mind to a study of the more important 
theories and principles connected with the steam-engine. Much 
more might have been said here, but the space available for a 
review is necessarily limited, and we can only now conclude this 
brief notice by strongly recommending the work before us to all 
more advanced students of steam and of the steam-engine. 
Improvements in certain Iron-work. By Messrs. Hoopes and 
Townsend. 
This little work not being provided with a title, we have been 
obliged to provide it with one of our own invention. It is a 
notice of the trade specialities of the firm from whom it pro- 
ceeds — such as “ key-stone ” boiler-rivets, cold punched nuts, 
&c. It contains a Report, by Prof. R. H. Thurston, on the 
results of experiments performed at the Stevens Institute of 
Technology, in order to decide the comparative resisting power 
of “ cold-punched ” and “ hot-pressed ” nuts. The former, ac- 
cording to the figures quoted, showed a marked superiority. 
The Speaking Telephone and Talking Phonograph , and other 
Novelties. By George B. Prescott. Fully illustrated. 
New York : D. Appleton and Co. 1878. 
Mr. Prescott is already favourably known, both in this country 
and America, as the author of an excellent Manual of Electricity 
and Telegraphy : but we are sorry to say that the present work, 
although valuable in its way as a record of faCts, is not calcu- 
lated to add to his reputation as a scientific writer. It consists, 
for the most part, of verbatim reprints of most of the papers on 
telephony and kindred subjects which have been read before the 
different scientific societies of England and America during the 
last two or three years, loosely strung together, and interspersed 
with a few remarks from the author. These papers are all printed 
in the same type as the original matter, and as inverted commas 
