364 Notices respecting New Books. 



intelligible and in some cases fairly good, but wherever an}' shading 

 has been attempted the detail is entirely obscured and the figure ren- 

 dered almost or quite worthless. As examples of this, the diagrams 

 of the pulley-blocks (p. 379) and of the speed-counter (p. 535) 

 may be mentioned, though these are not chosen as being con- 

 spicuously bad. In other cases the figure is spoiled by a too great- 

 similarity between different parts of the apparatus, as in the 

 ammeter (p. 466), where the coil conveying the current and the 

 controlling horseshoe permanent magnet are drawn so as to look 

 exactly like two parallel coils ; or, again, in the sketch of Poggen- 

 dorfPs method of comparing electromotive forces (p. 531), in which 

 the traditional diagram has been departed from, and a very 

 remarkable series of circles put in its place. 



It is to be regretted that the work of the engraver has been so 

 badly executed, since the book is on this account debarred in a 

 great measure from use by any except those who have access to 

 the actual apparatus described (presumably that of Harvard Uni- 

 versity). The text and the order in which the experiments are 

 given are both good, and maintain the standard of the first volume. 

 We find in many experiments special devices referred to winch 

 should materially help to increase the degree of accuracy obtain- 

 able. As an instance we may mention the use of the micrometer- 

 screw to measure the amount of bending of a loaded beam ; the 

 point of the screw touching the beam closes an electric circuit and 

 rings a bell. Some few omissions have, as we think, been made ; 

 nothing is said, for example, about the water voltameter, although 

 the direct comparison of the electrochemical equivalents of, say, 

 copper and hydrogen, is a very easy, satisfactory, and instructive 

 experiment, the results of which are independent both of the 

 constancy of tbe current used and of its duration. Moreover, the 

 experiment affords a good example of the correction of the volume 

 of a gas for temperature and pressure. 



In our perusal of the book we nave noted one or two misprints 

 in the text, which will scarcely lead to mistakes or confusion, 

 except, perhaps, in the description of experiment 98, where 

 Leclanche is spelt Lechanche throughout. A dash is omitted in 

 each of the formula) (5) and (6), p. 441, and in the lower formula 

 of page 563 the d should be t in order to accord with a previous 

 formula there referred to. 



James L. Howard. 



The Steam- Engine considered as a Thermodynamic Machine : a 

 Treatise on the Thermodynamic Efficiency of Steam-Engines, illus- 

 trated by diagrams, tables, and examples from practice. By J. H. 

 Cotterill, F.R.S. (Loudon : E. & F. X. Spon, 1890. Pp. xi 

 + 426.) 



The first edition of this work was published in December 1877, 

 and was intended " to serve as an introduction to applied thermo- 

 dynamics, while at the same time an attempt was made to study, 



