ON RAIL-KOADS.

265

diminution in the consumption of the fuel, the quantity permile be reduced below 51.55, then the diminished quantitycan be substituted in its stead, and the formula will stillrepresent the quantity with different loads.

The reader will scarcely expect that I shouldagain recur to the subject of friction, after theexperiments already detailed. It may appearhowever, to some, and I know it has alreadybeen made the subject of discussion, that,when the steam in the boiler is of a degree ofelasticity equal to 50lbs. per square inch ofsurface, that, in estimating the power of theengine, the same degree of pressure should becalculated upon the surface of the piston ; andthat the difference between the amount of suchpressure, and the actual performance of theengine, is the measure of the friction, or, as itis termed, of “ the power lost.” I must confessthe difference between the two effects at firstappeared great; but, on considering the methodby which the steam is transmitted from theboiler to the cylinders, and by also subjectingthe engine to experiment, the cause soon be-came very evident; and, when I found that thesame law operated in other high-pressure en-gines, the reason could then no longer be thesubject of mystery.

in all high-pressure engines, acting solely bythe elasticity of their steam ; and, indeed, in