ON RAIL-ROADS.

189

east-iron, and 15lbs. between it and the brass,which is equal to the difference between thecommon and the case-hardened wheels, andamounting to nearly the 550th part of theweight. This is not the only evil producedby the use of this kind of bearing ; it alsooperates very powerfully in cutting the axles.On being shewn two axles, it is readily distin-guishable to which kind of bearing each hadbeen subjected; the axle with the narrowhearing is cut and furrowed, while the other issmooth and even ; and it need not be stated,the effect which such a cause would produce inthe expence, by the destruction of axles.

The reduction of friction, by these twocauses, are very considerable, and, when pro-perly estimated, are of great moment in theeconomy of Rail-road conveyance. The tw o to-gether amounts to the 275th part of the weightof the carriage, and equal to 43 per cent, of thewhole amount of friction.

The following are some experiments which1 made upon the Hetton Colliery Rail-road, inDecember, 1824, which ascertaining the fric-tion by other methods, will be interesting as acomparison with the preceding. Length ofplane 1164 feet, perfectly straight, with anuniform and regular descent of one yard in104.24 or 11 feet 2 inches in the whole distance.