stances the use of electricity is the only possible way of handling the traffic. The second reason is the invariable one, in this commercial age, for all engineering enterprise—that it pays.
The development of the engineering methods by which the electrical operation of railways has been made possible is largely due to the first of the reasons mentioned above. Beginning with the electrification of the Mt. Royal Tunnel of the B. & O. Railroad, in 1896, there have been an increasing number of tunnel and terminal projects which have made use of the possibilities of electric operation in the way of increased traffic and freedom from smoke and gases of combustion. One conspicuous instance, the Grand Central Terminal in New York city, illustrates the typical limitations of tunnels and terminals which have rendered electric operation necessary. In 1903, an act of the New York Legislature was passed providing for the operation before July 1, 1908, of all trains into Grand Central Station by some form of motive power not involving the combustion of fuel in the motive units. This action was aimed directly at the elimination of smoke and gases in the tunnels leading to the terminal. The results of the adoption of electricity have in this respect entirely justified expectations. Passengers may now occupy observation platforms in passing through these tunnels which were formerly notorious for their danger and discomfort.
There was, however, an additional reason why it was necessary to adopt a motive power other than steam in the New York terminals. Traffic into the Grand Central Station is limited by the number of tracks in the tunnels. The minimum three-minute headway between trains operated by steam fixed the maximum traffic at forty trains per hour each way. The capacity of the terminal with this limitation of service was taxed to its utmost and some relief for the increasing traffic was imperative. Owing to the improved conditions of electric operation, trains may be run on a two-minute headway or less, thus increasing the station capacity by more than fifty per cent. The conditions in the New York tunnels are typical and other conspicuous instances of similar installations are those of the B. & O., at Baltimore, the St. Clair tunnel of the Grand Trunk Railway and a three-mile tunnel on grade on the Great Northern Railway. The Illinois Central Railroad is about to electrify 325 miles of track, comprising the approaches to its Chicago terminals.
The elevated lines of New York city are an additional instance of the necessity of adopting some other system than steam in order to increase the capacity for traffic. The continued growth of the population of New York city has far surpassed that of the traffic facilities for transportation within the city. As measures for relief the elevated and surface lines were equipped with electricity and in addition the subway system was constructed. Within three years following the adoption