2^2 XMPROVEMEKT IN THE CONSTRUCTION 



vr. 



Short Account of Mr. Arthur IVoolfs Improvement in the Con- 

 JiruSiion of Steam-Engiitex. 



pifcovery that iVJlR. WOOLF founds his improvements on an important 

 ^Tte'fufered ^'''^o^'^'')' '^^ '^^s made refpeaing tlie expaisfihilit)' of fteam 

 to expand, with when increafed in temperature beyond the boiling point, or 

 y^H' powerful 212° of Fahrenheit's thermometer. It has been afrertained 

 ' for fome time by Mr. Watt, that fteam ading with the ex* 



panfive force oF four pounds per fquare inch againft a fafety- 

 valve expofed to the atmofphere, is capable of expanding it- 

 felf to four times the volume it then occupies, and ftill to be 

 equal to the pretfure of the atmofphere. Mr. Woolf has dif- 

 covered and eftabliftied by proof, that fleam of the force of 

 five pounds the (qnare inch, may expand ilfelf to five limes its 

 volume; that n-^^alles or quantities of fteam of the like expan- 

 five force of fix, feven, eight, nine, or ten pounds the fquare 

 inch, may be fud'ered to expand to fix, feven, eight, nine, pr 

 ten limes its volume, and will flill be refpeftively equal to 

 the atmofphere, or capable of producing a fafhcient action 

 againft the pifton of a fleam-eng:ne to caufe the fame to rife 

 in (he old engine (with a counterpoife) of Newcomen, or to 

 be carried into the vacuous pnrt of the cyljnder in the im- 

 proved engines firft brought into eflecl by Metfrs. Boulton and 

 Walt; — that this ratio is progreffive, aud nearly if not quite 

 uniform^ fo that fteam of the expanfive force of 20, 30, 40^, 

 or 50 pounds the fquare inch of a common fa!et) -valve will 

 expand itfelf to 20, 30, 40, or 50 times its volume wiih like 

 effect; and that, generally, as to all the inlermediale or 

 higher degrees of elaftic force, the number of times which 

 fteam of any temperature and force can expand itielf is nearly 

 the fame as the number of pounds it is able to (uliain on a 

 fquare inch expofed to the c(>rnnion atniofpheric prcffure: pro- 

 A'ided always that the fpafe, or veflel in which it is allowed to 

 expand itfelf, be of the fame temperature as that of the lleam 

 before it was allowed room to expand. 

 *-thc increafe of Refpeding the ditl'erent degrees of temperature required 

 tempeiacurcnot {^ b^jng fteam to, and maintain it at, different expanfive 

 able. forces above the weight of the atmofphere, Mr. Woolf has 



3 found. 



