THE AGE OF ELECTRICITY
263
first line to be so transformed was the Mersey Railway, the change being made in May, 1903. As this line for the most part is underground, the steam trains were objectionable on account of the smoke nuisance in the tunnel. It is significant that during the period of steam traction this line was not financially successful, but since the change the line has been very prosperous. The success of the City and South London Railway made it possible to raise capital for similar projects, and gradually the extensive and ramified system of the Underground Electric Railways Company of London was evolved. Like the Mersey Railway the Metropolitan District Railway, which throughout its steam age was largely a financial failure, has, as a result of electrification and co-ordination with the other London " Underground " lines, been transformed into a dividend-paying concern. " Considered as a whole the results prove that where there is the potentiality of large traffic, electricity is the instrument which must be applied. During the steam days the most crowded part of the District Railway (the Inner Circle) carried a maximum of sixteen trains per hour. With electric traction that figure has been raised to forty trains per hour. It may be accepted as substantially proved that on suburban and interurban railways in populous districts electric traction is a means of increasing traffic and diminishing the proportion of working costs. Moreover these results have been achieved in conjunction with substantial reductions in fares and with marked improvements in the comfort of travelling."* Electric traction has also been applied to suit special requirements, as, for instance, mountain railways having^ steep gradients. The first mountain railway constructed in the United Kingdom was 4I miles in length, running from Laxey to the summit of Snaefell with a gradient of 1 in 12 for practically the entire length. The line was opened for public use in 1896. Another special application is the transport of goods over short distances by means of electric trucks. Certain types of self-contained passenger and other electric automobiles have been developed which do not require wires. In the selfcontained electric vehicle the power supplied to the motor is * Wiiyte,
Electricity in Locomotion,
iog.