Necessity has given birth to another useful invention. Patrons of the trolley cars have often observed the exasperating habit which trolleys have of sometimes leaving the wire unbidden and the serious damage which is often done to the car tops while these otherwise indispensable adjuncts of the service are executing a war dance in mid air. Chas. Stevenson, one of the conductors of the D., Y. & A. A., tired of this sort of thing, has devised an attachment which bids fair to check the mad career of the festive trolley the moment that it slips away from its regular duties. The attachment is nothing more than a spring window shade roller on a large scale attached to the rear of the car. When the trolley leaves the wire the spring which holds it against that wire naturally throws it higher and the recoil does the damage. In this case the rope attached to the trolley is attached to the spring roller, as the string is attached to a shade roller. The first wild jump of the trolley, when it leaves the wire operates the same on the new devise as the slight jerk of the hand does on the shade roller and in less time than it takes to tell it the slack rope is rolled upon the roller and the trolley is bound as fast as a wild steer in a cowboys lasso.