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FRICTION OK CARRIAGES

fastened to the carriage, the friction of whichwas the subject of experiment, in the same man-ner as represented in the drawing. Manuallabour was then applied to the dynamome-ter-carriage to push it along the Rail-road,and the rope being fastened to the waggon,it was also drawn forward. The distancewhich the pendulum was drawn out from theperpendicular, by the action of the rope, was,therefore, the measure of force or pressurerequired to move the waggon forward uponthe Rail-road.

Before recording the pressure, indicated bythe index, both carriages were put into a cer-tain velocity, and that velocity was kept upas equable as possible during the course ofthe experiment. At first it was found ratherdifficult to preserve a state of perfect uniformvelocity, the least variation in the force appliedto push the dynamometer forward, causingthe index to vibrate backwards and forwards ;by employing a greater number of men,we accomplished, after successive trials, aregularity of action, which produced the mostuniform velocity in the motion, and each ex-periment was repeated until we were perfectlysatisfied of the accuracy of the result.

The degree of force, indicated by thedynamometer, was, therefore, that which was