34 



NATURE 



[March i i, 1909 



ordinary design being weak to resist the torsional 

 moments to which the)' are subject. The last chapters 

 are devoted to the cost of machining and the 

 factors which govern it, to the construction of the 

 " characteristic " diagram for any given headstock, 

 and the means of measuring from it the economic 

 value of the design. In the last chapter, by way of 

 illustration, the authors show the application of the 

 torque-speed diagram, and the lathe characteristic to a 

 series of selected lathes built by well-known makers. 



The book will be indispensable to the lathe designer, 

 and to the manufacturer who employs large numbers 

 of these machine tools ; it is an admirable example 

 of the way in which scientific research in our engineer- 

 ing schools can be applied to advance and improve the 

 great manufacturing industries of the country. 



(2) This is a revised edition, in part re-written, of 

 Prof. Church's well-known text-book on the mechanics 

 of engineering. The book is divided into two sections, 

 one dealing with the mechanics of solids, the other 

 with the mechanics of fluids, and a separate index 

 has been provided for each section ; the first section 

 is again divided into three parts : the first part treats 

 of statics, the second kinetics, while the third and 

 most important part, covering 320 pages, deals with 

 the subject of the strength of materials. 



The chief changes in the subject-matter in this 

 edition are confined to certain chapters on the strength 

 of materials, and to portions of the section treating 

 of the mechanics of fluids. An important new chapter 

 is that devoted to the flexure of reinforced concrete 

 beams, a subject of much interest to engineers engaged 

 in structural design ; the author considers that for 

 purposes of practical design it may be assumed that, 

 as in homogeneous beams, cross-sections, plane before 

 flexure, remain plane when the beam is slightly bent; 

 this assumption is only valid if the modulus of elas- 

 ticity of concrete is constant in value ; this is not so, 

 but, as the author points out, it does not vary much 

 in value within the limits of stress to which such 

 reinforced beams are subjected in good design work. 



Other useful fresh matter is that contained in 

 chapters xii. and xiii. ; in the former the subject of 

 the flexure of simple and continuous beams is treated 

 from the geometrical standpoint ; that is, algebraic 

 relations are deduced from the known properties of 

 certain geometrical figures ; this leads to a very simple 

 and available form of the three moments theorem ; 

 in the latter there is a concise and lucid discussion of 

 the relations between stress and strain in thick 

 cylinders. In the section of the book dealing with 

 hydraulics, the chief additions are those describing 

 new appliances, such, for example, as the Cippolletti 

 or trapezoidal weir, the Vcnturi meter, and the differ- 

 ential manometer. 



Te.xt-books dealing with the mechanics of engineers 

 are constantly being consulted by practical men, who 

 wish to refresh their memory in regard to the theory 

 of some particular problem which they meet with in 

 their professional work, and for this purpose a very 

 complete index is essential. In any further re-issue of 

 this work, it would be a distinct improvement if the 

 indices were made more thorough and complete. 

 NO. 2054, VOL. 80] 



(3) As in part i., this book is divided into two main 

 sections, one dealing with the mechanism of the car, 

 the other with its management, and, in addition, there 

 is a brief general introduction on the subject of elec- 

 tricity. As the book is intended rather for users of 

 cars than for builders, the description of the car 

 mechanism has been written in such a way that any 

 intelligent non-technical reader should have little diffi- 

 culty in appreciating the important points to which 

 attention must be paid in design, and as to which 

 the buyer must also be able to satisfy himself before 

 deciding to purchase an electric car. In dealing with 

 the management of the car, the author describes two 

 forms of brake suitable for the measurement of the 

 power of the motor, but he does not describe the 

 simpler rope brake, which is much more satisfactory 

 for such tests than the Prony friction brake, especially 

 if, instead of a rope, a thin, hollow, flat band of metal 

 is used through which a constant stream of water 

 can be circulated to absorb the heat generated by the 

 friction. 



Special attention has been given to the manage- 

 ment of the battery, since success in driving an electric 

 car depends so much upon the manner in which the 

 battery is handled. In regard to the cost of running 

 in London an electric car, fitted with pneumatic tyres, 

 the author estimates that it will average with a good 

 driver 2'92(/. per car mile, the cost of the electric 

 energy only amounting to o'i2d., wear and tear of 

 tyres accounting for I'jd., depreciation of battery 

 for i'2d., the other expenses amounting to o'id. The 

 last chapter of the book is devoted to petrol-electric 

 vehicles, that is, to vehicles which combine with the 

 motor and controller equipment of an electric car 

 a petrol engine and a dynamo driven by it to supply 

 electricity to the motor; this system possesses certain 

 important advantages, and is being applied with 

 success to commercial vehicles and omnibuses. 



As soon as the battery problem is solved, the elec- 

 tric car will, at any rate for town use, rule supreme 

 — but we are a long way yet from solving that 

 problem. T. H. B. 



BIOLOGY FOR TEACHERS. 

 First Course in Biology. Part i., Plant Biology. 

 Pp. XXV 4- 204, and 302 figures; Part ii.. Animal Bio- 

 logy. Pp. 224, and 408 figures; Part iii., Human 

 Biology. Pp. 164-l-x, and 132 figures. By L. H. 

 Bailey and VV. M. Coleman. (New York : The Mac- 

 millan Co. ; London : Macmillan and Co., Ltd., 

 1908.) Price 7i-. 6d. 



THIS book hails from across the Atlantic, and aims 

 at supplying a course of work intermediate be- 

 tween unorganised nature-study and the formal science 

 of the more advanced courses. The general intention 

 of the authors is : — 



" To lay greater stress on the processes and adapta- 

 tions of life as expressed in plants and animals and 

 men, and to attach less importance to botany, zoology 

 and physiology as such." 



It is certainly well (hat teachers should do their 

 utmost to prevent that study of botany which leaves 

 the student ignorant and indifferent to the plants 



