NA TURE 



409 



THURSDAY, MARCH 2, 1899. 



ELECTRICITY AND RAILWAYS. 

 Applications oj Electricity to Railway Working. By 

 W. E. Langdon. Pp. xvi + 331. (London : E. and 

 F. N. Spon, Ltd., 1897.) 



IN this book the author shows that he is well 

 acquainted with the subject on which he writes, and 

 that his knowledge is of a thoroughly practical char- 

 acter ; we can, therefore, recommend it not merely to 

 those who are professionally engaged with railway work- 

 ing, but also to that portion of the public who take an 

 interest in the various methods that are adopted for 

 securing their safety, and administering to their comfort, 

 when they are travelling by rail. 



The book opens with a chapter " on the construction 

 of a line of telegraph," in which cogent reasons are 

 advanced why, in the making of a new railway, the com- 

 pany ought to face the initial expense of constructing 

 good, rather than cheap, telegraph lines ; and the results 

 of a " penny wise and pound foolish " policy are pointed 

 out. 



The language used in this chapter — indeed throughout 

 the book — recalls the telegraph engineer of thirty years 

 ago in that force and expressiveness, rather than elegance 

 or exactness, are the result aimed at. The older 

 engineer, for example, speaks of the "railway metals" 

 when he means the iron rails, " metalling a road" when 

 he means laying down stones, and the " metal " of an 

 insulator when he is referring to the porcelain cup, and 

 not, as a person might imagine, to the iron stalk of the 

 insulator. Sentences like — " Iron arms formed of L-iron 

 . . . are less costly than the tubular arm, but fall short of 

 the degree of strength which the latter enjoy," the portion 

 of the arm earth-wired is practically covered, &c.," "a 

 9-feet sleeper will cut three stay blocks, say each 36 

 inches by, &c.," invest iron and old railway sleepers with 

 an activity that certainly has the effect of giving life to 

 the book. The " D.\'. insulator," we are told, is a 

 "double Varley," and so we realise that it is not a pious 

 reference to the wishes of Providence ; but how many of 

 the average readers will be able to guess what such 

 crisp expressions as " G.L wire ' and "G.P. wire" stand 

 for? 



Chapters ii., iii., and iv. deal with " surveying," "posts 

 and wires," and "telegraph instruments and batteries" 

 respectively. The use of the telephone to replace tele- 

 graphic signalling is dealt with, the practicability of em- 

 ploying the same line wire for the block bell and the 

 telephone, on not very busy sections of the railway, is 

 pointed out, and the methods of running several circuits 

 on the same telegraph poles so that there shall be little 

 mutual induction between them are described. The 

 author doubts the advantage of replacing Leclanche cells 

 with dry cells, but quotes the results of tests which show 

 that of the two the dry cell polarises less rapidly than 

 the Leclanche cell when each is joined up in series with 

 a resistance of 100 ohms, or "short-circuited" through 

 a resistance of 100 ohms, as the author incorrectly 

 calls it. 



Much is told us in Chapter v., and told us well, about 

 NO. 1531, VOL. 59] 



"block signalling," of which there are three methods in 

 actual use, viz. the positive, the affirmative, and the 

 permissive. With the first the signal is left indicating " line 

 clear," except when a train is actually on the section in 

 advance ; with the second the signal is normally left " line 

 blocked," and it is only on information being telegraphed 

 forward by the signaller that a train desires to enter a 

 section, and on the signaller in advance telegraphing back 

 his consent, that the semaphore arm is lowered. With 

 the third system, two, or more, trains going in the same 

 direction are allowed on one section at the same time, 

 but the rear trains are warned that there are other trains 

 in advance. This last system, which can hardly be 

 called a block system at all, is, however, only employed 

 under exceptional circumstances, such as in the working 

 of station-yards, to enable trains to be brought to a stand 

 at their respective platforms, for interchange of traffic, or 

 for connection with other trains. 



The affirmative system is the one generally employed 

 with the railways in this country, but on the Metropolitan 

 Railway it is found necessary to resort to the positive 

 system, in consequence of the large number of trains ; 

 so that the semaphore-arm being up indicates that there 

 is actually a train on the section ahead. 



We may take this opportunity of noticing, although 

 Mr. Langdon does not refer to the matter in his book, 

 that the behaviour of the ordinary railway passenger 

 furnishes a striking example of the absence of powers of 

 observation that characterises the average person. A 

 train is at rest, say, at the platform of a Metropolitan 

 Railway station, and the danger signal is obviously up, 

 yet the passengers tear down the stairs, and rush 

 frantically along the line of carriages only to wait, 

 panting for breath, until the train starts. Again, 

 we wonder how many copies have been sold of the 

 photograph of "the Flying Dutchman going at sixty 

 miles an hour," and how few are the purchasers who have 

 noticed that in this photograph the signal is against the 

 train, so that it must have been at rest when the photo- 

 graph was taken. Or, again, how many persons who 

 obtained season tickets for the Inventions Exhibition 

 remarked that the train stamped, in gold, on the cover of 

 the ticket was running neither on the " up" nor on the 

 " down " pair of rails, but on one of each pair, so that 

 there was a single odd rail left on each side of the train 

 for some mysterious and unknown use. 



The animated character of the instruments in this 

 chapter is almost suggestive of Rudyard Kipling, for 

 Mr. Langdon says that the tongue of a relay "obtains 

 its magnetic life from a permanent magnet H," and that 

 the indicating portion of an apparatus is locked "in the 

 position last afforded it by the current." 



The block instruments devised by Preece, Pryce and 

 Ferreira, Spagnoletti, Tyer, Webb and Thompson, and 

 others, are fully dealt with in Chapters v. and vi., while 

 Chapter vii. brings us to "automatic block signalling" 

 with which the passage of a train works the signal elec- 

 trically or electro-pneumatically. This subject has made 

 practically no progress in this country, for while Hall's 

 automatic system, requiring only a comparatively small 

 battery for each section of the line, is largely used on the 

 United States railways, it is only on the Liverpool Over- 

 head Electric Railway, where there is plenty of electric 



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