412 



NATURE 



[September 29, igio 



pressure, 200 lb. per square inch. This engine practically 

 reached the limit of the construction-gauge. 



An acceleration of thirty miles per hour in thirty seconds 

 is considerably below what may be applied to a passenger 

 without fear of complaint. But it is clear that it is just 

 about as much as a locomotive can do with a train of 

 reasonable weight. Even with a gross load of 300 tons 

 nearly one-third of it is concentrated in the locomotive, 

 leaving only 200 tons to carry paying load. The problem 

 of quick acceleration cannot therefore be properly solved 

 by means of a steam locomotive. But with electric trac- 

 tion the limitations imposed on the locomotive by the con- 

 struction-gauge and by the strength of the permanent way 

 are swept away. 



The equivalent of the boiler-power of a dozen locomotives 

 can be instantaneously applied to the wheels of the electric 

 train, and every axle in the train may become a driving 

 axle. Thus the whole weight of the stock, including the 

 paying load, may be utilised for tractive purposes. If, for 

 instance, the train weighed 200 tons, then a tractive force 

 equal to one-fifth of this, namely, 40 tons, could be 

 exerted on the train, but uniformly distributed between 

 thi- several wheels, before slipping took place. The 

 ■problem of quick acceleration is therefore completely 

 solved by the electric motor. 



Electric Railu'ays. 



December 18, 1890, is memorable in the history of 

 railway enterprise in this country, for on that date the 

 City and South London Railway was opened for traffic, 

 and the trains were worked entirely by electricity, although 

 the original intention was to use the endless cable system 

 of haulage. This line inaugurated a wonderful system 

 of traction on railways, in which independent trains, 

 moving at different speeds at different parts of the line, 

 are all connected by a subtle electric link to the furnaces 

 of one central station. 



Since that epoch-marking year electric traction on the 

 railways of this country has made a gradual if somewhat 

 slower extension than anticipated. But electrically 

 operated trains have in one branch of railway working 

 beaten the steam locomotive out of the field, and now 

 reign supreme— that is, in cases, as indicated above, where 

 a quick, frequent service is required over a somewhat 

 short length of road. The superiority of the motor over 

 the steam locomotive, apart from questions of cleanliness, 

 ■convenience, and comfort, lies in the fact that more power 

 can be conveyed to the train and can be utilised bv the 

 motors for the purpose of acceleration than could possibly 

 be supplied by the largest locomotive which could be con- 

 structed within the limits of the construction-gauge. There 

 are many other considerations, but this one is funda- 

 mental, and determines the issue in many cases. 



A few facts relating to the present state of electric rail- 

 ways in the United Kijigdom may prove of interest. .\t 

 the end of iqo8 there were in the United Kingdom 204 

 miles of equivalent single track worked solely by elec- 

 tricity and 200 miles worked mainly by electricity, corre- 

 sponding to 13S miles of line opeii for traffic. Of this, 

 102 miles belong to the tube railways of London and 201 

 miles to the older system formed by the District and the 

 Metropolitan Railways and their extensions. 



It is not an easy matter to ascertain exactly how much 

 ■capital is invested in these undertakings for the purpose 

 of electric working alone, since some of the lines originally 

 ■constructed for a steam locomotive service have been con- 

 verted to electric working. On the converted lines there 

 is the dead weight of capital corresponding to the loco- 

 motive power provided before electrification took place. 

 The capital invested in the 102 miles of tube railways in 

 London is a little more than 25,000,000?. 



The total number of passengers carried (exclusive of 

 season tickets) on the 138 miles of electrical track during 

 the year 1908 was nearly 342 millions, being roughly one- 

 third of the total number of passengers carried on all the 

 railways of England and Wales during the same period. 



The average cost of working this traffic is 22-3<J. per 

 train-mile. This figure includes the service of the lifts, 

 which is presumably returned with the traffic e.tpenses. 

 The charges work out in this way : — 



NO. 2135, VOL. 84] 



T.ABLE n'. 



Average Worl^ing Cost per Train-mile of the Electric 

 Railivays worked wholly or maiitlv by Electricity in 

 Engluiid and Hales for the Year 190S. 



Pence per 



Locomotive power ... ... ... ... 8-40 



Repairs and renewals of carriages and 



waggons ... ... ... ... ... 1.50 



Maintenance of permanent way ... ... 2.40 



Traffic expenses ... ... ... ... ... ^.22 



General charges ... ... ... ... ... "1.52 



Rates and taxes ... ... ... ... ... 2-36 



Government duty o-o88 



Compensation ... ... ... ... ... o-ii6 



Legal and miscellaneous ... ... ... 075 



Total 



"■35 



The corresponding total receipts were 38-(i5d. per train- 

 mile. The working expenses are thus 58 per cent, of the 

 total receipts. Comparing this with the figures given 

 above for the whole of the lines in England and Wales, it 

 will be seen that the cost for locomotive power on the 

 electric railways appears to be about two-thirds of the 

 cost on steam lines per mile run, the cost for repairs and 

 renewals of carriages and waggons about one-half, and 

 the cost for traffic expenses about one-half. 



The two kinds of working are no. however, strictly 

 comparable, as all the conditions of traflic in the two 

 cases are different, and the length of the electric lines is 

 relatively so small that the problems which arise out of 

 the transmission of electric power over long distances are 

 excluded. The traffic expenses and the cost of repairs and 

 renewals of carriages and waggons, general charges, &c., 

 are practically independent of the kind of power used for 

 locomotive purposes, and, moreover, the difference in 

 weight of electric trains and the steam-hauled trains is 

 on the average so great that no comparison can be insti- 

 tuted without ton-mile statistics.^ 



Method of Working. 



With two exceptions, the method of working the 

 electrified lines of this country is in the main the same. 

 A third conductor rail is laid on insulators fixed to the 

 ordinary track sleepers, and is maintained throughout 

 the whole of its length at as nearly as possible a pressure 

 of 600 volts, except in a few cases where the pressure is 

 500 or 550 volts. Collecting shoes sliding along the rails 

 are fixed to the trains, and through them current is sup- 

 plied to the armatures fixed to or geared with the axles. 

 The current flows through the armatures back to the 

 stations or sub-stations through the running rails, which 

 are bonded for the purpose, or sometimes through a fourth 

 rail carried on insulators fixed to the track sleepers, as in 

 the cases of the District and Metropolitan Railways. 



Differences in the equipment arise out of the geographical 

 necessities of the distribution. For a short line the power 

 is produced at a central station, and is distributed by 

 feeders to the conductor rail direct. For longer lines 

 power is produced at higher voltage (11,000 volts in the 

 case of the District Railway), and is then distributed to 

 sub-stations conveniently placed along the line, where it 

 is transformed to a lower voltage, converted to direct 

 current, and then by means of feeders is distributed at 

 600 volts or thereabouts to the third rail. 



In 1908 the Midland Railwa\- Company opened for 

 traffic the electrified line connecting Lancaster, More- 

 cambe, and Heysham. The method of electrification was 

 a departure from the general direct-current practice 

 hitherto applied to electrified lines in this country. Power 

 was supplied to the trains at 6600 volts, single phase, at 

 twenty-five alternations per second, along an overhead 

 conductor. The pressure was reduced by transformers 

 carried on the motor-coach itself, and was then used by 

 single-phase motors. The traffic conditions on this line 

 are simple. 



1 Most valuable information regarding the cost of con\ertinK the line 

 between Liverpool and Southport from stepm to electric wciking will 

 be found in Mr. Aspinall's presidential address to the Institution of 

 Mechanical Engineers. 



