200

FRICTION OF CARRIAGES

space agree with that actually passed over.This might be expected, as the calculatedspace is derived from the descent of the samecarriage during a calm, (see Experiment V.)where the space passed over was nearly thesame, and, consequently, the effect of the air,in retarding the velocity of the one, would beequal to the effect of the wind in acceleratingthe other, when the velocities became equal,and that velocity corresponded with the velo-city of the wind.

Not having an opportunity of making theexperiment upon this piece of road during acalm, I selected a short distance of the Kil-lingworth Rail-way, with a nearly uniformdescent, and embraced an opportunity of tryingthe experiment, when there was scarcely anywind, or at least so little that it could haveno sensible effect, either in retarding or acce-lerating the velocity of the carriage. Thedescent of plane was not uniformly the samethroughout the whole length, but, to ascertainthe true result, I took the actual descent at theend of the several spaces passed over.

The following table will show the result:—