174

FRICTION OF CARRIAGES

the entire basis of the subject. Observationshave been made on the weight a horse couldovercome, when placed upon a carriage ona Rail-road ; but as we had no measure ofthe force exerted by the horse, the resistance ofthe carriage could not be thereby ascertained.

Mr. Grimshaw, of Sunderland, when pro-prietor of a colliery in that neighbourhood,made a great many experiments on the fric-tion of wheel-carriages, with the particularsof which I have been favored. He laid acast-iron rail-way down, upon beams of wood,and placed upon this rail-way the carriagesused by him in conveying his coals downto the river. He then elevated those beamsat one end until they formed different angleswith the horizon, and observed the time thecarriages were in descending from one endto the other, when the plane was elevatedto different angles. By comparing the spacesactually passed over by the carriage, withthe space which gravity would have causedthe body to describe, in the same time, whenfalling freely, the amount of retardation causedby the friction was thus ascertained.

The result was as follows:—

Loaded carriage, weighing altogether 8522Ibs. friction-equal to 50 lbs., or the 170th part of its weight.