Necessily has given birtb to another useful invcution. Patrons of the troloy cars have of ten observed the exasperating babit whioh trolleys have of ometimes leaving the wire unbidden -jnd the serious damage whioh is often done to tbe car tops while these otherwise indispensable adjancts of the service are execntiag a war dance io mid air. Chas. Stevenson, one of the oonduotors of the D., Y. & A. A., tired of this sort of tbing, has devised au ataohraeut whioh bids fair to oheck the ruad career of the festive trolley the moment thatit slips away from its regular duties. The attaohment is nothïug more than a spring window shade roller on a large scale attached to tbe rear of the car. When the trolley eaves the wire the spring which holds ït against that wire natnrally throws it ïigher and the reooil does the damage. [d this case the rope attauhed to the trolley is attaohed to the spring roller, as the string is attaohed to a shade roller. The first wild jump of the trolley, wheu it leaves the wire operates tbe same on the uew devise as the slight jerk of the hand does on the shade roller and in less time than it takes to teil it the slack rope is rolled upon the roller and the trolley is bonnd as fast as a wild steer in a cowboys lasso.