278 



NATURE 



[June i, 1916 



In the application of thermodynamics to 

 chemistry a method of purely mathematical 

 analysis may be adopted or the principle of the 

 efficiency of the perfect thermodynam.c engine 

 may be applied directly to physico-chemical pheno- 

 mena, as is done by Prof. Washburn, who, how- 

 ever, simplifies the usual procedure by devising a 

 specially constructed engine. 



The influence of a pressure-change on equilibrium 

 receives practically no quantitative treatment in 

 most text-books ; in this work it receives more of 

 the attention it deserves. The author discusses 

 the effect of extra pressure not only when applied 

 to all the phases, but also when applied to one 

 phase only. This last we consider of great im- 

 portance in elucidating so-called "osmotic pres- 

 sure," which is a special case of what we may 

 call one-phase pressure. 



Under the treatment of the influence of a tem- 

 perature-change on equilibrium we find no refer- 

 ence to Nernst's complete integration of the 

 differential equation, though Nernst's modifica- 

 tion of Trouton's rule is mentioned. On the other 

 hand, there is an excellent account of specific 

 heat, without, however, applying the quantum 

 theory. 



The chapters on electro-chemistry are decidedly 

 good, but we should prefer, for teaching purposes, 

 a different order. It would be better to have a 

 special chapter for E.M.F., which, so far as pos- 

 sible, should be kept separate from Faraday's 

 laws and conductivity. We hope that in future 

 editions the author will deal more fully with 

 potential differences at interfaces generally on 

 account of their importance in the theory of col- 

 loids; and for the same reason there should be 

 more about the mechanical forces at interfaces. 



Equilibrium, especially in solutions, is treated 

 with a thoroughness unusual in introductory text- 

 books. Mention is made of many recent advances 

 in physical chemistry, and valuable references to 

 literature help to make up for the rather scanty 

 account given of some sections of the subject. 

 There are brief biographical footnotes, numerous 

 cross-references, and problems for practice in cal- 

 culation. The printer's errors are few and not 

 at all serious. 



This excellent work is well worthy of the earnest 

 study of both teachers and students. 



Francis W. Gray. 



APPLIED MECHANICS. 

 (i) Elementary Applied Mechanics. By Prof. T. 

 Alexander and Prof. A. W. Thomson. Third 

 edition. Pp. xx + 512. (London: Macmillan 

 and Co., Ltd., 1916.) Price 155. net. 



(2) Applied Mechanics : First Year. By H. 

 Aughtie. Pp. 184. (London : G. Routledge 

 and Sons, Ltd., 1915.) Price 2s. net. 



(3) Textile Mechanics. By W. Scott Taggart. 

 -Pp. vii+117. (London: G. Routledge and 

 Sons, Ltd., 191 5.) Price 2s. net. 



(i) pROFS. ALEXANDER AND THOMSON'S 

 ^ " Elementary Applied Mechanics " is an 

 excellent treatise — a development of a much 

 NO. 24^1. VOL. Q7] 



smaller one which engineers knew thirty years 

 ago. It follows chiefly the methods of Rankine, 

 but with a larger use of graphic constructions. It 

 is a feature that the graphic diagrams are to scale, 

 and are, in fact, exercises worked out. Appended 

 to each chapter are examples fully worked out. 

 On the mathematical side and within its range 

 the treatment is complete. On the practical side 

 it is not quite so satisfactory. The data of 

 weights, working stresses, etc., involved in any 

 practical solution are very scantily given, and the 

 considerations which lead a designer to modify 

 purely theoretical results are little touched on. In 

 this the authors differ from Rankine, who took so 

 much trouble with the data that his values are 

 still of authority after fifty years, and are some- 

 times quoted in this book. For instance, the one 

 essential starting point in roof design is the magni- 

 tude and distribution of the wind pressure. The 

 authors merely assume a wind at 45° with the 

 rafter, on one side of the roof, with a normal 

 component 25 per cent, greater than the weight 

 of the roof at each joint. But the wind pressure 

 has nothing to do with the weight of the roof, and 

 its distribution is not that assumed. 



The problem of rolling loads on bridges is 

 treated fully and with originality. The bending- 

 moment diagram of circular arcs is interesting and 

 useful. The maximum moment for any section for 

 any travelling loads is fully discussed. The 

 moving model which draws the bending-moment 

 curve for a trolley is very ingenious, but it seems 

 to us more difficult to follow than the ordinary 

 demonstration. 



On the subject of earth pressure Rankine 's fric- 

 tional theory is followed, without reference to the 

 reservations he himself makes or to the numerous 

 investigations which have shown how in most 

 ordinary cases, except for dry sand, it is not even 

 a good approximation. For retaining walls the 

 deviation of the centre of pressure from the centre 

 of the joint is taken at 3/ioths of the width with- 

 out any explanation. It is a critical point, and 

 needs defence. 



Long struts are treated well, but only by the 

 use of the Gordon-Rankine formula. The authors 

 say that Rankine proved Gordon's formula to be 

 rational. This is disputable; it is really an inter- 

 polation formula between Euler's and that for 

 short columns. The various formulae which are 

 more convenient in use, and are, in fact, largely 

 used in design, are not referred to. 



Arched ribs are treated by Levy's graphic 

 method, and there is an interesting and original 

 chapter on masonry arches, though, perhaps, the 

 treatment is too abbreviated to be very useful. 

 Curiously, reinforced arches, now so important 

 and affording such excellent scope for scientific 

 treatment, are not alluded to. 



The treatise is excellently printed and illus- 

 trated, and will certainly be useful to students and 

 engineers. It seems a defect that the book has 

 only a table of contents and no index. 



(2) This is a very elementary book, in which 

 ordinary mechanics, kinematics of machines, and 

 some problems in work and power are treated 



