NATURE 



169 



THURSDAY, DECEMBER 26, 1907. 



ELECTRIC TRACTION. 

 Electric Tractiou. By Prof. Ernest Wilson and Francis 

 Lvdall. Two vols. Vol. i., Direct Current, pp. 

 vii + 475; vol. ii., Alternating Current, pp. vii + 328. 

 (London : Edward Arnold, 1907.) Price i^s. nel 

 each. 



THERE is no announcement on the title-page that 

 this work is a second edition of a book which 

 appeared in 1S97. This omission, however, is fullv 

 justified, for although technically the present work 

 mav be considered a new edition, it is in reality a new 

 work. Progress during the last ten years has been 

 so great that to bring the work up to date it had 

 practically to be re-written and very greatly enlarged. 

 Even in its present form of two handsome volumes, 

 comprising together some 760 pages, the authors have 

 not treated the subject exhaustively. This statement 

 is not meant as a reproach, but simply as an illustra- 

 tion of the fact that the application of electric traction 

 to tramways and railways has become so many-sided 

 that an exhaustive treatise of the subject can hardly 

 be expected. All that can be expected is that the 

 authors should make a judicious selection of types 

 and systems, and this expectation is on the whole 

 fulfilled in the present work. 



There is, however, one rather important omission, 

 namely, the use of the three-wire system on direct- 

 current railways, as suggested by Krizik and carried 

 out by his firm on the Tabor-Bechyne line in Bohemia. 

 It is true that the authors give on p. 416 a sketch 

 of the circuits and a short description of the system 

 adopted on the City and South London line, which 

 is a three-wire system in the sense that the trains in 

 one direction are worked from a positive 500-volt trolley 

 and the trains in the other direction from a negative 

 500-volt trolley, but this is a far less advantageous 

 system than that devised by Krizik, where the positive 

 and negative side of the three-wire system are utilised 

 in the same train, and the earth or rail return is only 

 called into requisition in the event of a breakdown on 

 one side of the system. 



Of the two volumes the first is devoted to direct- 

 current and the second to alternating-current rail- 

 ways. The treatment is mainly descriptive, without 

 much criticism on the authors' part, and on the whole 

 there is a tendency to give prominence to .American 

 designs or to English designs of American origin. 

 This favouring of American work goes so far that 

 the authors, whilst referring to standardisation of 

 tramway motors as determined by the American In- 

 stitute of Electrical Engineers, completely ignore the 

 standard rating adopted by the International Associa- 

 tion at the 'Milan Congress last year. Possibly they 

 may think the American standard better, but that is 

 no reason why they should keep their English readers 

 in ignorance of the fact that there is a standard in 

 use on the Continent of Europe which will have to 

 be complied with by those firms who secure contracts 

 on the Continent. 



A little more than half of the first volume is given 

 NO. 1 99 I, VOL. yj] 



up to Ir.-iinway work, and deals in succession 

 with the motor, the controller, resistances, trolleys and 

 bows, rolling stock including brakes, the track, over- 

 head equipment, slot and contact systems, feeders, 

 generating stations, car sheds, storage-battery trac- 

 tion and regenerative control. .Approximately the 

 same order in the treatment of details is followed 

 in the part devoted to railways, with the addition of 

 a chapter on substations. Then follows a chapter on 

 cost of tramway woi-k, which, being taken from 

 actual practice, should prove very useful when getting 

 out preliminary estimates, also a chapter on working 

 expenses, traffic receipts and tramway accounts in 

 general, and finally there is an appendix giving all 

 the Board of Tr.ade regulations. 



.As already remarked, the treatment is mostlv de- 

 scriptive, but not always complete. Thus the suspen- 

 sion of tramway motors is dealt with in only four 

 lines on p. 78, and in the description of magnetic 

 brakes we miss the magnetic friction brake on the 

 axle, although magnetic track brakes are not only 

 well described but also critically compared. The 

 tables relating to turn-out, cross-over and transition 

 curves on pp. 112 to 116 are well arranged, and will 

 be found very useful in laying out the track. Also 

 the details of overhead equipment are well repre- 

 sented, but we miss the bridge wdre round the ears 

 which has of late years been introduced as a pre- 

 caution to avoid the trolley wire coming down in the 

 event of its breaking, which, as is well known, takes 

 place generally close to the ear. 



As regards buffer batteries, the authors seem to be 

 under the impression that Mr. Highfield made their 

 use possible by his automatic reversible booster. This 

 is not so. Buffer batteries have first been suggested 

 by Dr. Edward Hopkinson in 1S93 in a paper read 

 before the Institute of Civil Engineers on the City 

 and South London Railway, and very shortly after, the 

 first buffer battery was installed by the Tudor Accu- 

 mulator Co. in the power house of the Zurich tram- 

 ways, the economic success being so remarkable that 

 buffer batteries had become a quite regular feature in 

 tramway power houses on the Continent long before 

 .Mr. Highfield designed his very ingenious system of 

 boosting. 



On p. 197 the authors show a diagram (Fig. 144) 

 and call it a negative booster wrongly connected. In 

 this case the booster is supposed to be a series machine 

 driven at a constant speed. There is nothing wrong 

 about its connection ; the only wrong thing in the 

 diagram is the direction of the current as marked by 

 arrows. .A moment's consideration will show that if 

 the machine is run at the critical speed in relation to 

 the resistance of the return feeder, it is the very best 

 possible negative booster, since it will relieve the rails 

 from return current to even a greater extent than the 

 booster with excitation from the positive feeder. 



The authors' treatment of the complicated subject 

 of controllers is excellent. They always give first a 

 diagram showing the principle and then the actual 

 arrangement of circuits and contacts, thus rendering 

 the study of an intricate subject comparatively easy. 

 The same praise may be given to their way of working 

 out running diagrams and the determination of the 



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