176 
Steam Engine. 
said Arthur W oolfj do hereby describe and ascertain the 
nature of my said invention, and the manner in which the 
same is to be performed, as follows : that is to say, I have 
ascertained, by actual experiments, and have applied the 
same to practice, that as in practice it is found that steam 
acting with the expansive force of four pounds the square 
inch, against a safety-valve exposed to the atmosphere, is 
capable of expanding itself to four times the volume it 
then occupies, and still to be equal to the pressure of the 
atmosphere ; so in like manner steam of the force of five 
pounds the square inch can expand itself to five times its 
volume. Masses or quantities of steam of the like expan- 
sive force of six, seven, eight, nine, or ten pounds the 
square inch, can expand itself to six, seven, eight, nine, 
or ten times its volume, and still be respectively equal to 
the atmosphere, or capable of producing sufficient action 
against the piston of a steam-engine, to cause the same 
to rise in the old engine (with a counterpoise) of Newco- 
men, or to be carried into the vacuous part of the cylinder 
in the improved engines first brought into effect by Boul- 
ton and Watt : and this ratio is progressive, and nearly, if 
not entirely, uniform ; so that steam of the expansive force 
of twenty, thirty, forty, or fifty pounds the square inch of 
a common fafety-valve, will expand itself to twenty, thirty^ 
forty, or fifty times its volume ; and, generally, as to all 
the intermediate or higher degrees of elastic force, the 
number of times which steam of any temperature and 
force can expand itself, is nearly the same as the number 
of pounds it is able to sustain on a square inch, exposed 
to the common atmospheric pressure ; provided always, 
that the space, place or vessel, in which it is allow^ed to ex^ 
pand itself, be at least of as high a temperature, or nearlv 
as high a temperature, as that of the steam before it be 
allowed room to expand : that is, whatever be the degree 
of heat necessary to the pentianency of steam of the force 
