ON IMlL-liOAOJ.

245

convoy. Whence 61 4 . 239 4 . 360 -4- 17 — 677 lbs., the re-sistance which the engine is capable of overcoming bythe adhesion of the wheels at all times upon an Edge-rail -road without slipping.

The weight of the engine is about 16,800 lbs.,whence the amount of adhesion will be equal tothe 25 th part of the weight; and, as the frictionor adhesion will always be in proportion tothe pressure upon the rails, this expressionwill be constant, and will apply to engines ofdifferent weights.

Having thus ascertained the proportionwhich the power that enables the engine toeffect its progressive motion bears to itsw r eight, we can easily calculate the acclivities,which, with certain weights, will present resist-ances corresponding with this power. Thus,upon a level plane, the engine will overcomea j-esistance the amount of which is equal tothe 25th part of its weight ; or taking thefriction of carriages the 200th part of theirweight, a load equal to W of its weight. Ifthe acclivity of the plane, on which the engineis made to travel, be such, that the height isequal to the 25th of its length; then thewhole adhesion of the engine will be requiredto drag itself forward, and none will be leftfor the load; and, in all the intermediatedegrees of elevation, betw een a dead level and