198

FRICTION OF CARRIAGES

the liability to error was less, I lately made thefollowing experiments upon a certain stage, orpiece of Rail-road, selected for the purpose. Aperfectly straight plane of the Edge Rail-road, with a uniform and regular inclina-tion, was taken, the declivity of which wassuch as would cause the carriages to descendwith an accelerated velocity ; a carriage wasplaced upon it, and allowed to descend freely,and the space it passed over in successiveportions of time, was marked with the utmost,accuracy in the following manner—standingupon one end of the carriage, and aided byan assistant, at the end of every ten secondsI made a mark upon the plane where thecarriage happened to be, and afterwards mea-sured the distance between those marks, whichgave the space passed over in each successiveperiod. The carriage was first put in motionat the top of the plane, by a slight impulse, onlysufficient to overcome its vis inertia. Thedescent of the piano was 1 yard in 200 yards,

or 134 inches, in 13968 inches.