468
EXPOSITION AT VIENNA.
The locking-magnet N could be placed on a local circuit, to he opened and closed at n by the lever L. As a very slight weight would be sufficient to keep the disc in position of "arrest,” a slight force in the locking-magnet would seem to suffice to counterbalance it, and this force would be easily overcome by the stronger impulses given to the armature through the large magnet M. In this case the latter would be wound with small and the locking-magnet with large wire.
III. Signals of Warning at Grade Crossings of Common Roads.
There are no signals of this class on exhibition at Vienna, but the subject is too important to be passed over in a review of railway signals. Ordinarily in Europe, as I have said, gates are required to be kept at the crossing of highways, and they are generally closed in obedience to electrical signals sent from fixed stations.
The use of gates may be the only means of securing safety to those who cannot or will not take heed of optical or aural signals, and assure themselves ,that no train is near before crossing the track. Where signals are sent from fixed stations to the persons in charge of the gates, the large number of attendants required along a line where grade crossings are frequent, is a source of great expense to the railway. If several crossing signals are connected in one circuit, as is sometimes the case in France (see signals, class 1), an unnecessary delay may he caused to traffic on the highway.
The employment of gates is, therefore, not always desirable, or even practicable, in America. The frequency of accidents shows, however, that the means of prevention at present employed are not sufficient. When casualties of this kind are not due to the wilful carelessness of the traveller on the highway, they are generally occasioned either by his inability to see the approaching train or hear its signal, or by the neglect of the engineer to sound its whistle or bell in time.
What is wanted, therefore, is an aural or optical signal (or both), placed at the crossing, which shall be sounded or displayed without the aid of attendants whenever a coming train reaches a certain distance from it, and shall continue to sound or be displayed until the train has passed.