It is dear, that the power of the steam engine will de-
pend, upon the energy of the steam, — 1st Steam of two
atmospheres will, other things being equal, produce double
the eflect of steam of one atmosphere. — ^d. the force of the
steam remaining the same, the power of the engine will
depend on the extent of surface acted upon, that is on the
area of the piston. — 3d. these two circumstances remaining
the same, the power of the engine will depend on the
velocity with which the piston moves.
