May 31, 1877] 



NA TURE 



Woroschiloff upon the paths of conduction in the spinal 

 cord, for example), are confined to small print. Excep- 

 tion might also be taken to the somewhat dogmatic deci- 

 sion of an undecided question, such as that of the cause 

 of the pulse-dicrotism. And it may be doubted whether 

 the introduction, if not of pictures, at least of a greater 

 number of diagrams, would not render some of the sub- 

 jects easier to the comprehension of the student. But 

 loolced at as a whole, the book must be pronounced 

 thoroughly well done, admirably .adapted for its purpose, 

 and creditable alike to its author and to the science which 

 it is intended to promote. E. A. Schafer 



WEISBACH'S "MECHANICS OF 

 ENGINEERING" 

 A Mainml 0/ the jSIcihatiics of Eiigiiiccrine;, and of the 

 Construction of Machines, with an Introduction to the 

 Calculus, by Julius Weisbach, Ph.D. Vol. I. — Theo- 

 retical Mechanics. Translated from the Fourth Aug- 

 mented and Improved German Edition, by Eckley B. 

 Coxe, A.M. (London : Triibner and Co., 1877.) 



THERE is, perhaps, no book on mechanics so well 

 suited to the wants of civil and mechanical engi- 

 neers as the late Ur. VVeisbach's " Lehrbuch der Ingenicur 

 und Maschinen-Mechanik." In his preface to the first 

 edition of his work the author thus stated his design 

 (we quote from the translation before us) : — 



'" My principal effort has been to obtain the greatest 

 simplicity in enunciation and demonstration, and to treat 

 all the important laws in their practical applications with- 

 out the aid of tlic higher mathematics. If we consider 

 how many subjects a technical man must master in order 

 to accomplish anything very important in his profession, 

 we must make it our business as teachers and authors for 

 technical men to facilitate the thorough study of science 

 by simplicity of diction, by re.Tioving whatever may be 

 necessary, and by employing the best known and most 

 practicable methods. For this reason 1 have entirely 

 avoided the use of the calculus in this work. Although at 

 the present time the opportunities for acquiring a know- 

 ledge of it are no longer rare, yet it is an undeniable fact 

 that unless we are constantly making use of it, we soon 

 lose that facility of calculation which is indispensable ; 

 for this reason so many able engineers can no longer 

 employ the calculus which they learned in their youth. 

 As I do not agree with these authors who in popular trea- 

 tises enunciate without proof the more difficult laws, I 

 have preferred to deduce or demonstrate them in an 

 elementary, although somewhat in a roundabout manner." 



Weisbach was severely censured by some people for 

 attempting to treat his subject without the higher mathe- 

 matics, but he kept to his own way, saying that he in- 

 tended his work not as a university text-book, but only 

 for "practical men." In the later editions of his work, 

 however, he gave additional demonstrations of some of the 

 laws by the differential and integral calculus, on which 

 he also added an introductory chapter, which surpasses 

 in clearness anything we have seen on the subject. In 

 judging of Weisbach's m.ethod we must not forget that 

 few men had so much experience in teaching practical 

 engineers, and that no one had a better knowledge of 

 what such men really require ; and we must at least 

 acknowledge that, although in some few cases he may 

 have carried his system too far, and have sacrificed scien 

 tific exactness of expression to mathematical simplicity, if 

 he erred, he did so on the right side. Most English 



authors of books on mechanics and kindred subjects seem 

 to forget how small is the amount of mathematical know- 

 ledge possessed by the average engineer. In the rising 

 generation of engineers this is no doubt changing for the 

 better, but there are still many in this country — men of 

 ability and men who have executed works which do credit 

 to the nation— whose ideas of the diflerential and integral 

 calculus are vague in the extrem.e, and it is satisfactory 

 that there is at last a standard work for their use. 



The work appeared originally in two parts. The first 

 " Theoretische Mechanik," and the second, " Statik der 

 Bauwerke und Mechanik der Umtriebsmaschinen." To 

 these was afterwards added a third, " Mechanik der 

 Zwischen und Arbeits-Maschinen." The volume before 

 us is a reprint of an American translation of the fourth 

 German edition of the " Theoretische Mechanik." This 

 edition was published in 1863. In 1875, after the author's 

 death, a fifth edition was issued, which differs to a small 

 extent from the fourth. It contains a chapter on springs) 

 taken principally from Reuleaux's " Construction und 

 Berechnung der fiir den Maschinenbau wichtigsten 

 Federarten;" another on the general principles of 

 dynamics, also, in the Appendix, " The Elements of 

 Graphical Statics," none of which are in the fourth edition. 

 We regret that the chapter on graphical statics was 

 not added to the translation. The graphical method 

 seems likely to come more generally into use, and a short 

 introduction to it, giving the general rules for its appli- 

 cation to statics, and showing the manner of using it, 

 would have added to the value of the book. 



Mr. Co.xe has done the work of translation carefully, 

 and, on the whole, well. He has avoided the blunders 

 made by the author of the former translation, and he 

 has given a faithful lendcring of the German. He uses, 

 however, many terms which are not in use in this country, 

 and we are sorry that they are far from being improve- 

 ments. He talks, for example, of the centre of gravity of 

 lines and geometrical figures, of " living forces " (surely 

 VIS viva was quite bad enough), &c. There is room for 

 difference of opinion as to whether Mr. Coxe has done 

 wisely in retaining the various tables in the book on the 

 metric system. 



This translation is wonderfully free from misprints, and 

 most of those which do exist are quite apparent. On 

 p. 479, for example, we find the following : — '' Rem,4RK. — 

 Under the supposition that the proof strength increases 

 and decreases with the ultimate strength, the English 

 engineers increase the size of that portion of cast-iron 

 girders which is subject to compression," &c. (the italics 



are ours). On p. 121, § 21, t/ = — (—'') should be: 

 V = -— , and " The clement of time t (tit)" should 



be : The element of time t = <i t. On p. 291, § 157, we 

 have: "From this we obtain QH = U R.tan.cp=dR." 



Then on the line below " -L. . _,whichislhe difference," 

 t> //' ' 



&c. This should be 0R= OR. tan. (j> = OR.L .K.. ''■ 



Weisbach's name is known in this country principally 

 in connection with hydraulics. In this branch of mecha- 

 nics he was a most laborious experimentalist, and he 

 obtained many valuable results, many of which are incor- 



