NA TURE 



341 



THURSDAY, JUNE 28, 1917. 



THE ELECTRIFICATION OF OUR 

 RAILWAYS. 



Electric Traction: A Treatise on the Application 

 of Electric Power to Tramways and Railways. 

 By A. T. Dover. Pp. xix-667-r5 folding 

 plates. (London: Whittaker and Co., 1917.) 

 Price 185. net. 



IN electric traction the questions that have to 

 be discussed may be broadly classified under 

 two headings — technical and financial. The 

 author touches on the latter class incidentally, 

 and then only because it is impossible to 

 leave financial considerations out of account 

 altogether. In the former class he has not 

 included descriptions of generating stations and 

 transmission lines. Even with these restrictions, 

 however, it is only by the severest compression 

 that he has managed in a single volume to give 

 the necessary descriptions of the line, the rolling 

 stock, the appliances and apparatus used in elec- 

 tric traction, and to touch on most of the tech- 

 nical and theoretical considerations involved. 

 We congratulate the author on having succeeded 

 in writing a treatise which engineers and 

 advanced students will find most useful. He is 

 evidently well read in the literature of the sub- 

 ject, most of which is published in the Proceed- 

 ings of various engineering societies and technical 

 journals, both in this country and- abroad, and is 

 therefore inaccessible to many. 



In Britain railway electrification is mainly con- 

 fined to large cities and their immediate neigh- 

 bourhood. In most cases this traffic has been 

 stimulated by the necessity of competing with 

 tramcars and motor-omnibuses. Unless the 

 railway companies are content to give up a large 

 fraction of the suburban traffic, they must adopt 

 the expedient of electrifying their lines. This 

 expedient, although costly, has proved success- 

 fixl, and many people wonder why the English 

 railways do not at once set about electrifying 

 their main lines. They say that electrification is 

 bound to come, and point out that morally it is 

 wicked to go on burning coal extravagantly in 

 locomotives, seeing that our coal resources will 

 certainly not last for ever. It will be w-ell, there- 

 fore, to {X)int out some of the reasons which are 

 making engineers hesitate. 



On suburban lines the stations are close 

 ; together and the trains are continually starting 

 I and stooping. Under these conditions an 

 1 electric train, owing to its higher schedule speed, 

 I can carry a larger number of passengers in a 

 I given time than a steam train having equal seat- 

 , «ng accommodation. The number of signal and 

 j train movements required for an electric train 

 ! entering and leaving a terminus is only one- 

 I quarter of the number required for a steam train, 

 j and for this reason a much larger traffic can be 

 I handled^ by the electric trains before the traffic in 

 "^he station gets congested. 



I NO. 2d.87. VOT.. ool 



For main-line railways the problem is more 

 difficult. The efficiency of a modem steam loco- 

 motive is very high, and when it has to haul a 

 fast passenger train over a long distance on a 

 level track it is working at its very highest 

 efficiency. The cost of the electric locomotive 

 that could replace it is very heavy, and when we 

 take into account the interest on the great initial 

 expense of electrifying the line, the saving 

 effected, if any, is very small. If, however, there 

 are heavy gradients on the line or long tunnels, 

 electric traction may prove much the more 

 economical. On a steep gradient the potential 

 energy of an electric train can be converted into 

 electrical energy and pumped back into the line- 

 On the Giovi-Genoa line of the Italian State Rail- 

 ways, for instance, the energy recuperated on the 

 down grade is from 60 to 80 per cent, of the 

 energy consumption by the same train on the up 

 journey. The results of tests on a train equipped 

 with motors connected for "regenerative con- 

 trol " on the Metropolitan Railway in Paris show 

 a saving of 20 per cent, of the energy consumj>- 

 tion. In addition, the adoption of regenerative 

 control effects appreciable economies In the 

 maintenance costs of the brake shoes, wheel 

 tyres, and rails. The saving in the rails is an 

 especially important item. 



Unfortunately, there are several different elec- 

 trical systems for railways, of which the most 

 important are the direct-current, the three- 

 phase alternating-current, and the single- 

 phase alternating-current systems. There are 

 numerous able advocates of each of these 

 systems, and they can instance in support of their 

 contentions commercially successful electric rail- 

 ways. It is of vital importance to the future of 

 a railway that it should choose the right system 

 of electrification at the start, for the advantages 

 of interchange of traffic between railways are 

 obvious. In the interests of the country' there is 

 a pressing need for standardising an electric 

 traction system as soon as possible, and so we 

 hope that the usual costly period of waiting for 

 the survival of the fittest will be brief- For this 

 reason we welcome books of this type, which will 

 enable railway engineers to appreciate the rela- 

 tive advantages and disadvantages of the various 

 svstems and so help them to come to a decision. 



The author starts with a short and accurate 

 introduction to the mechanics of train movement. 

 It is an excellent example of one of the practical 

 uses of the theory' of dynamics taught in all our 

 schools. We next come to chapters discussing 

 in an instructive way various kinds of direct- and 

 alternating-current motors. The modern methods 

 of testing and controlling them are given. Half- 

 way through the book we come to chapters 

 describing the rolling stock for tramways and 

 railways, electric locomotives, and track and 

 overhead construction for tramways and raih\ays. 

 The last two chapters are on feeding and dis- 

 tributing systems and on substation converting 

 machinery respectively. In addition, numerous 

 examination questions are set, the answers being 



