4IO 



XATURIi 



[March 2, 1899 



power available, thai aulomatic block signalling has 

 found a footing in C.reat Britain. To work Timmis' 

 "long-pull electromagnet " used on this line "the energy 

 required is 5 amperes at a pressure of 40 volts (200 

 watts} "—at least so says the author of this book, making 

 the same sort of confusion between current, energy and 

 power as characterises " Article 12 of the Programme of 

 the International Competitive Trials of Accumulators for 

 Road Traction," which has just been published, and 

 which states : " Besides an ammeter measuring the total 

 quantity of electricity supplied to and from the batteries 

 as a whole, an energy meter wattmeter) . . . will 

 measure the quantities of energy absorbed by and 

 supplied to each of them." 



Unlike automatic block signalling, the interlocking of 

 the mechanical devices, and of the electric and me- 

 chanical devices, connected with signalling and shunting, 

 has received much attention in Great Britain during the 

 past twenty-nine years, the earliest attempt in this 

 direction having been made in 1870 by the author himself 

 in conjunction with Mr. Preece, and a large number of 

 illustrations connected with this part of the subject 

 renders the study of Chapter viii. instructive. Some of 

 the illustrations, however, are drawn on too small a scale, 

 and are not well enough executed to enable the reader 

 to clearly understand all the details. 



In the next chapter signal repeaters, light indicators, 

 train indicators, lightning protectors, &c., are dealt 

 with. A signal repeater is a device for indicating 

 whether the motion of the arm of a semaphore, which is 

 out of sight, corresponds correctly with the motion given 

 by a signalman to the handle in his box, while a light 

 indicator informs him whether the lamp on a semaphore 

 post has gone out, or has become dim. The action of 

 the latter depends on the difierence in the expansion, by 

 heat, of a tube of brass and of a rod of s/eci inside it ; 

 this, however, is not clearly explained, and from the 

 description it would appear as if the action would lake 

 place just as well if the tube and the rod were of the 

 same material. These indicating devices are found to 

 be of great use, says the author, " at heavily signalled 

 termini." 



"Electric station lighting" and "electric train 

 lighting" come next, and the author mentions that 

 while arc-lighting of goods-yards-sidmgs is now much 

 used, since it effects economy in capital, men, material 

 and time in loading trucks, it was originally introduced 

 in the Nine Elms yard m linly to stop the robbery which 

 the absence of efficient lighting encouraged, and that the 

 cost of its installation there has been largely defrayed 

 by the diminution of the loss through theft that has 

 resulted. 



The author, like so miny practical men, talks about 

 " the volts and current," although doubtless he would 

 not say "the feet and weight of a girder" when he 

 meant " the length and weight," nor would he speak of 

 " the pounds of the main boilers," although he does not 

 hesitate to write " the volts of the main dynamos." 

 Since ihe jrcneric name current is regularly employed, 

 without reference to any particular unit of current, why 

 should not the expression '^pressure," "■ poU'n/ial differ- 

 ence," " F.D.," or some other generic name, be simi- 

 larly used. "Current and pressure" if you like, or "am- 

 NO. I 53 I, VOL. 5Q] 



peres and volts" if preferred ; but, great as may be oui 

 respect for the lineman on a railway, or for the switchboart 

 attendant in an electric light station, it is not compulsori 

 for us to form our technical langua^'e by slavishly copy- 

 ing his "current and volts." 



To produce a Board of Trade unit inclusive of al 

 charges excepting those for land, taxes and depreciatior 

 of buildings, costs the Midland Railway Company (tt 

 whom Mr. Langdon is the electrical engineer) from 

 2'3i/. at the Birmingham Central Station to y-,d. at tht 

 Leeds Hunslet Station. These amounts, although much 

 higher than the corresponding sums at a London large 

 electric light-generating station, are fair, in view of the 

 short time that artificial lighting, even in the winter, 

 is required in a railway goods yard, or in offices which 

 close at 5.30 p.m. 



The subject of lighting railway carriages interests 

 every one— or ought to. But the public have for many 

 years tolerated the lamp being placed at the middle of 

 the roof of the cotnpartment of a railway carriage instead 

 of at the back of the reader, and no e.xpression of feeling 

 was manifested when the fixing of penny-in-the-slot 

 accumulators and reading-lamps In the carriages on the 

 Metropolitan District Railway suggested the principle 

 that the Company did not undertake to light even the 

 first class compartments in return for the sum paid for 

 the passenger's ticket. 



The author suggests— and we think rightly— whether 

 "it might not yet be advisable to attach to each train a 

 vehicle equipped for the double duty " of lighting and 

 heating, " having for its primary source of power an oil 

 engine." 



The short Chapter xii. on " Intercommunication in 

 trains in motion " we may pass over — for the author has 

 recently dealt with that subject at length in a paper read 

 before the Institution of Electrical Engineers — and we 

 come to the last, on the "administration of the en- 

 gineering branch." In this the author suggests (probably 

 unintentionally) the explanation of the special literary 

 style adopted In his book, for he says : 



" When we write a letter the conventionalities of 

 society demand a degree of courtesy which is readily 

 excused, and which would seem absurd In a telegram. 

 It is not clear why it should be so ; why a letter — 

 especially a lousiness letter — should not be just as accept- 

 able If couched in the same concise terms considered so 

 proper for telegraphic correspondence.' 



We conclude as we commenced by expressing the 

 opinion that, in spite of minor blemishes such as we 

 have referred to, Mr. Langdon's book Is distinctly good 

 on the whole. For of what consequence are a few 

 antiquities of expression, and how easy Is It to be critical 

 now, and to suggest improvements In the work of men 

 of the older si liool which can be made to d,iy, when we are 

 revelling amidst a wealth of electric meters, ammeters, 

 voltmeters, coulomb-meters, walt-metcrs, energy meters, 

 potentiometers, &c., and are enjoying the luxury of the 

 labour-savins.; appliances with which technical colleges 

 are ei|uippc'.l ; Will, however, the young electrical 

 engineer of to-day, with all this vast collection of electrical 

 appliances al Ills command, succeeil In m. iking so deep an 

 impress on ckctro-technlcal science as did men like Mr. 

 Langdon thirty years (ii,'*', and will a practical electrical 



