336 Patent for certain Iiuprovememii 



■with the expansive force of four pounds the square inch, 

 affainst a safety-valve exposed to the atmosphere^ is ca- 

 pable of expanding itself to four times the volume it then 

 occupies, and still to be equal to the pressure of the atmo- 

 sphere ; 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 expansive force of 

 six, seven, eight, nine, or ten pounds the square inch, can 

 expand itself to six, seven, eight, nine, or ten times its vo- 

 lume, and still be respectively equal to the atmosphere, or 

 capable of producing suflicient action against the piston of a 

 steam-engine, to cause the same to rise in the old engine (with 

 a counterpoise) of Newcomen, or to be carried into the va- 

 cuous part of the cylinder in the improved engines first brought 

 into effect by Boulton and Watt : and this ratio is progres- 

 sive, 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 saiety-v^alve, will expand itself to 

 twenty, thirty, forty, or fifty tmies its volume; and, gene- 

 rally, as to all the intermediate or higher degrees of elastic 

 force, the number of times which steam of any tempera- 

 ture 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 conn"non atmospheric pressure ; provided 

 always, that the space, place or vessel, in which it is 

 allowed to expand itself, be at least of as high a tempera- 

 ture, or nearly 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 permanency of steam of 

 the force of twenty pounds the square inch, if steam of 

 that force be employed, the space, place, or vessel in which 

 it is allowed or intended to expand itself, should be of the 

 same temperature, or nearly so ; and so with steam of 

 any other power, as of thirty, forty, or fifty pounds the 

 square inch, the space, place, or vessel in which it is to 

 expand, should be at or about the same degree of heat as 

 steam of the force employed requires for its existence; in 

 Avhich case, as I have before stated, steam can expand itself 

 about as n)any times as the number of pounds it could have 

 sustained on a square inch as aforesaid, before it is allowed 

 to expand or dilate itself. Here, however, it may be ne- 

 cessaVy to remark, that in stating this ratio I only speak of 

 the expansion of steam as it can be managed and commanded 

 in practice, and not of the absolute expansion which per- 

 haps might be obtained if mechanism could be made so 

 perfeel as to prevent all escape of steam, and all partial con- 

 densation 



