316 Mr. Genet’s Reply to Dr. Jones. 
more used, or of the high pressure engine, (in which, on ac- 
count of its overwhelming foree, the pressure of the atmos- 
phere is not taken into acconnt, and the cylinder is left open 
to the air,) for the unfuir purpose of showing that my paral- 
lel was incorrect, and my definition of the steam-engine inju- 
dicious. Had he known, or candidly considered, that in the 
open ended cylinder the direct force of the steam goes 
to raise the piston, and that the expansive force of that steam 
being condensed, the vacuum created determines the fall of 
the piston, under its own weight and the incumbent pressure 
of the atmosphere, equal, on every square inch of the area of 
the piston, to 15 pounds, he would not have asserted, “that 
the pressure of the atmosphere and the weight of the piston 
were not necessrry to Mr. Watts’ engine, and served only to 
ract from its power.” 
= _ The . ‘is in’ reality no pressure of the atmosphere in Mr. 
Watts’ double acting engine,* which Dr. Jones has here in 
* Except on the area of the section of the piston rod.—Ep. 
