NA TURE 



193 



THURSDAY, DECEMBER 30, 1897. 



MOTIVE POWER AND GEARING. 

 Motive Power and Gearing for Electrical Machinery. 

 By E. Tremlett Carter, C.E., M.I.E.E., &c. Pp. xxii 

 + 620. (London : The Electrician Printing and 

 Publishing Company, Ltd.) 



MR. CARTER has written a very interesting and 

 very useful book on a subject of much importance 

 for electrical engineers. The needs of electrical practice 

 have had a great effect in stimulating the invention of 

 quick-running steam engines, the improvement of gas 

 engines, and the discovery of modes of transmitting 

 power from the driving machine to the driven which did 

 not formerly exist. An electrical engineer is all the better 

 electrical engineer for being also a good mechanical 

 engineer ; but as he must master (if he is to be anything 

 but the veriest rule-of-thumb mechanic) in the course of 

 his training in the class-room and the workshop, a very 

 considerable body of more purely electrical knowledge 

 and practice, and, over and above, acquire some know- 

 ledge and experience in mechanical matters, the latter 

 is the point in which, when starting on his practical 

 career, he is apt to be most deficient. 



Of course, for making all these things realities to a 

 man, there is no education for the engineer like that of 

 the workshop, provided his theoretical training in the 

 principles of the scientific work he is to do (for scientific 

 it ought always to be, or he is no true engineer), is carried 

 on at the same time, just as for the scientific study of 

 physical science there is no training like that of the 

 laboratory carried on parallel with systematic "discussion 

 of physical theory and experiment in the lecture-room. 



The electrical engineer, as we have observed, however, 

 if properly trained, has always an inquiring spirit, and 

 an observing eye, and an adaptability of self to circum- 

 stances, which enable him as he goes on in his work, and 

 comes into contact with the considerable diversity of 

 machinery which it is his lot to encounter, to gradually 

 become a mechanical engineer of great resource and 

 skill so far, at any rate, as his own department of work 

 is concerned. 



A book like Mr. Carter's, studied in connection with 

 workshop practice by a capable man, or kept on the shelf 

 in the dynamo room to be read and consulted when 

 time or the requirements of work present opportunity 

 cannot but be of great service. The topics dealt with 

 are many and various, and an enumeration of them 

 would more than occupy all the space at our disposal, 

 though it would bring out very clearly how great is the 

 range of mechanical question and device with which the 

 electrical engineer is now concerned. 



The first chapter deals with fundamental principles, 

 such as motive power, work, energy and its sources, 

 inertia, waste power and useful power, load and load 

 diagrams, dynamometry (more properly ergometry), and 

 storage of energy. The order of treatment differs some- 

 what from that which in a complete discussion of such 

 subjects would be regarded as logical, but it is, so far as it 

 goes, quite scientific, though the ideas referred to are 

 occasionally so general as to require a good deal of 

 NO. 1470. VOL. 57] 



special discussion and elucidation, which of course must 

 be obtained elsewhere. 



In the discussion of reciprocating (or simple harmonic) 

 motion, it would have been well to insert besides the 

 statement that the numerical ratio of the acceleration to 

 the displacement is a constant, that the value of this 

 ratio is j^ti^l'Y'^ where T is the period of the motion. This 

 is a simple rule which is of real service in dealing with 

 vibrations. The phrase " elastic forces of inertia '' seems 

 a little strange to the pure physicist ; but of course what 

 the author is insisting on, is the give and take action of a 

 body, which in consequence of its inertia stores up energy 

 in an accession of speed, and restores it again when the 

 speed is diminished. 



A beginning is made in this chapter of the important 

 subject of the measurement of power. One or two forms 

 of brake and of transmission dynamometer are described, 

 and the general principles discussed, the further treat- 

 ment being left till the systematic application of tests 

 comes under review. 



In this chapter also, it ought to be mentioned, the 

 author treats of economy of design. Lord Kelvin's law 

 of economy, though acted on to some extent, is not yet, it 

 is to be feared, fully appreciated and acted on. It says 

 really that improvement cannot be economically carried 

 beyond the point at which the proper animal charge for 

 the capital invested in an improvement of plant, is just 

 equal to the annual saving effected by making it. Here 

 is a point, of course, at which increase in the cost of 

 materials and labour retards, and diminution in the same 

 facilitates, improvement in design. 



After a statement of the problem to be solved, which 

 he puts in the form, " What are the best provisions which 

 may be made for utilising the available energy for the 

 performance of useful work and the production of a pay- 

 ing revenue ? " the author proceeds to deal with the 

 steam engine. This forms Part ii. of the work, and is 

 treated under -the headings: Fuels, thermodynamics, 

 principles, steam, furnaces and boilers, theory and action 

 of the steam engine, steam engine details, some typical 

 steam engines, steam engine driving, the steam engine 

 in relation to electric power, the management of steam 

 plant. 



After this enumeration of chapters, it will not appear 

 surprising that this part comprises more than half the 

 book by some twenty-two pages. All the chapters seem 

 to us full of practical information, and of great value to 

 electrical engineers. The sketch of thermodynamics 

 given is perhaps that which is most directly open to 

 criticism, not so much on account of what is included as 

 of what is left out. There are, however, one or two 

 points on which we would offer one or two slight 

 remarks. First it would be well always, if the phrase 

 "perfect gas" is to be used, to offer some direct de- 

 finition of its meaning. Mr. Carter does so in his p. "Ji- 

 Practically what he defines as a perfect gas is one which, 

 under all conditions, fulfils the characteristic equation 

 PV/T = constant. But in the definition of T there seems 

 a little looseness. Thus it is stated (same page), " taking 

 the zero on the Fahrenheit scale as the standard it was 

 found by Charles, that all gases expand 1/460 of their 

 volume at this temperature when raised from any 

 temperature to a temperature 1° F. higher." Then from 



K 



