January 3, 1895] 



NATURE 



219 



danger of the work in the hands of the learner who is 

 not in a position to sift the wheat from the chaff and the 

 weeds ? 



We do not think that this book will serve to advance 

 the reputation of its author, nor to advance agriculture. 

 We submit that " advanced agriculture" is not agricul- 

 ture plus a smattering of chemistry, a dip into geology, a 

 pinch of botany, a skim of entomology, a sniff at meteor- 

 ology, and so on ; even if the sciences be correctly ex- 

 pounded. The text-book of agriculture, like that of other 

 subjects, has no doubt to pass through stages of evolution, 

 and we trust it will not long remain at the stage indicated 

 by this book. 



EWING ON THE STEAM ENGINE. 



The Steam Engine and other Heat Engines. By 

 Prof. J. A. Ewing, M.A., B.Sc, F.R.S., M.Inst.C.E. 

 (Cambridge : The University Press, 1894.) 



ENGINEERING students and others will welcome 

 the present volume as one likely to increase their 

 knowledge of an important branch of engineering, from 

 the pen of an acknowledged master of the science ; 

 any work by Prof. P2wing is sure to be read by engineers 

 generally, and treated as a book for constant reference. 



As is well known, Prof. Ewing wrote some valuable 

 articles for the " Encyclop;tdia Britannica " on this sub- 

 ject, and it is an expansion of these articles which consti- 

 tutes the basis of this work. As a University text-book 

 this volume will fill a great want, treating as it does, 

 from the theoretical side, a subject only descriptively 

 dealt with in the majority of such text-books. As 

 the author remarks ; " The endeavour throughout has 

 been to make evident the bearing of theory on practical 

 issues." 



The first six chapters may be said to contain the early 

 history of the steam engine, and a scientific treatment of 

 the general behaviour of steam in the cylinder, as well as 

 the general theory of heat engines. The information 

 thus brought together is of a valuable nature, and the 

 references which are made, add considerably to the 

 usefulness of the work. To the thoughtful practical 

 engineer, this portion of the book will form a perfect 

 mine of matter for careful consideration. 



The testing of steam engines has of late years become 

 a common occurrence, thanks to Profs. Kennedy, 

 Osborne Reynolds, and many others. Designers and 

 manufacturers of such engines have everything to gain 

 by such experiments ; few being, like the late Mr. 

 Willans, capable of carrying out scientifically accurate 

 trials of their own engines. Chapter vi. deals with this 

 important question. Many useful hints are given, and 

 sources of error carefully pointed out. As indicator 

 diagrams play such an "important part in the trials of 

 steam engines, it is interesting to note that the Crosby 

 Company's modified form of Richards' Indicator is con- 

 sidered by Prof. Ewing to be one of the best. 



Compound expansion comes in for very full and accu- 

 rate treatment ; many sets of indicator diagrams are ex- 

 plained and illustrated, and the difficult matter involved 

 in the combination of such diagrams is lucidly dealt 

 with. Of the advantages of compound expansion in the 

 NO. 13 14, VOL. 51] 



use of high-pressure steam, we are told much, and also of 

 the mechanical advantages of such an arrangement. We 

 cannot help pointing out that, in this matter, the practical 

 men on the Clyde were singing the praises of compound 

 engines before the theoretical men would admit of their 

 utility or economy. On valves and valve gears our 

 author has much to say, although we notice nothing re- 

 markable in the chapter. Locomotive engineers do not 

 trust entirely to the drawing-board or calculation in the 

 design of valve gears. It is now the practice to try the 

 proposed gear as a full-size model on the valve gear 

 testing machine, and so to obtain the best results. The 

 latest machine of this kind has been erected in the 

 drawing-office of Messrs. Sharp, Stewart, and Co., the 

 eminent locomotive engineers, of Glasgow. The saving of 

 time is great, and very accurate results are obtained. In 

 fact, in such drawing-offices, the old valve diagrams, with 

 their many curves, are things of the past, and a simple 

 table of leads, cut-offs, suppressions, &c., for the different 

 degrees of expansions, has taken their places. 



Chapter ix. treats of the many forms of governors 

 used for regulating the work done in the steam engine, 

 commencing with Watt's simple arrangement, and finish- 

 ing with the differential or dynamometric governors in- 

 vented by the late Sir W. Siemens ; and further on in the 

 book we find much useful information concerning the 

 work on the crank shaft. Diagrams of crank efforts are 

 given, and the effect of friction and of the inertia of the 

 reciprocating pieces are duly discussed. The balancing 

 of machinery is an all-important subject, in fact the life 

 of any machine depends upon the balancing of its 

 moving parts ; for this reason, we are sorry to see 

 that Prof. Ewing has so little to say on this subject 

 generally, and particularly on the balancing of loco- 

 motives. If theory is of any help to the locomotive 

 engineer at all, surely it could be best applied in 

 balancing ; some engineers balance the whole reciprocat- 

 ing weight, others none ; the majority about 30 per cent.: 

 which is right ? Prof. Ewing does not help us, but 

 observes that " the final adjustment of the balancing 

 masses is usually a matter of experiment, the locomotive 

 being hung in chains to allow its oscillation to be 

 observed " ; this, to say the least of it, is never done in 

 this or any other country. 



The production of steam is the subject treated in the 

 following chapter ; the illustrations of the different boilers, 

 with the descriptions, are e.xcellent. The only specimens 

 of water-tube boilers illustrated are the Thornycroft and 

 the Babcock and Wilcox, the latter used principally for 

 stationary engines. The Thornycroft boiler is the fore- 

 runner of similar types ; for instance, the Yarrow and the 

 Clyde among others, all of which are considerably 

 lighter than the ordinary marine boiler. As an example 

 of the locomotive boiler, one of the London and North- 

 western Railway Company is taken as typical of British 

 practice. As an example of an injector for feeding 

 boilers, an old-fashioned type of Giffard injector is 

 illustrated, but more recent types arc described. 

 Mechanical stoking and the use of liquid fuel are also 

 mentioned. 



The following chapters, conclude the work, occupying 

 some sixty pages with descriptions of forms of steam 

 engines, air, gas, and oil engines. The Willan's central 



