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Dawn of the Electric Traction Era 103 employed, partly owing to the character of the soil which had to be penetrated, and the shallow type of railway was favoured — that is, placing the lines only a few feet below the street level as in the case of the Metropolitan Railway of London. In these instances, construction was carried out from the street, which was opened up to enable the necessary excavations to be made. The tunnel was then roofed in, the steel covering being supported by pillars, and on this metal roof the road was remade. While the construction of these special electric railways was under way the application of electric traction to the main lines was taken in hand. At first the efforts were far from pretentious, electricity being introduced to ameliorate conditions provoked by steam working, or to enable heavier, longer, and more trains per hour to be handled. One of the first conversions of this character was com- pleted in 1895, when the tunnel at Baltimore (U.S.A.), which is set upon a steep gradient, and in ascending which the steam-hauled trains were often forced to a stop owing to the weight of the train being beyond the power of the locomotive, was electrified. In this instance the superiority of electric working was so pronounced that the conversion of other tunnels was taken in hand, notably the Cascade tunnel upon the Great Northern Railway of America and the St. Clair tunnel of the Canadian Grand Trunk Rail- way. From such an unpretentious beginning the electrical engineer advanced to greater fields. In 1903 came the electrical operation of all trains pass- ing in and out of the New York City terminus of the New York Central Railway, followed later by similar