Then the retardation, caused by the frictionof the whole, will bew s
Theorem (13) F G — — 428lbs., the friction of the
engine and carriages. By Experiment V. we have the friction ofthe carriages 43 X 5 = 215lbs.; whence 428 — 215 = 213 lbs.,the friction of all the moving parts of the engine.
The resistance of the engine, when movedalong, and not subjected to the pressure of thesteam, will then be 213 lbs .; of this, taking thefriction at the 200th part of the weight, 100 lbs.will belong to the axles and the action of thewheels upon the rails, leaving 113 lbs. as thefriction of the pistons, connecting chain, andother rubbing parts of the engine.
The total friction, however, when employedin dragging a load after it, or that part of thepower required to produce a progressive motionin the engine itself upon the road, when loadedwill be different, and will be greater than whenthe simple motion of its parts only are con-cerned. When loaded with a certain resistance,the whole of that weight or pressure has to betransmitted from the impelling to the impelledpart of the engine, or from the pistons to thewheels upon the rail, through all the interme-diate parts; and this pressure, acting upon allthe various parts of the engine, forming theconnection between these two points, will