5# On the Ujc of Steam 



Specific difft rcnce in the iritcnfity of that force in thofe fub- 

 flances. 



But to return to the fubject more immediately under con- 

 federation. As it is effential that the fleam employed in heat- 

 ing liquids, in the manner before defcribed, fhould enter the 

 containing veflel at, or very near, its bottom, it is evi- 

 dent that this ileam mud be fufficiently ftrong, or elaftic, to 

 overcome, not only the preflure of the atmofphere, but alfo 

 the additional preffure of the fuperincumbent liquid in the 

 vefi'el ; the fteam -boiler mud therefore be made ftrong enough, 

 to confine the fleam, when its elaflicity is fo much In created 

 by means of additional heit, as to enable it to overcome that 

 refinance. This increafe of the elaftic force of the fteam need 

 not, however, in any cafe, exceed a preflure of five or fix 

 pounds upon a fqnare inch of the boiler, or one-third part, 

 or one-half, of an atmofphere. 



It is not neceffary for me to obferve here, that in this, and 

 alfo in ail other cafes where fleam is ufed as a vehicle for 

 conveying heat from one place to another, it is indifpenfably 

 neceffary to provide fafety- valves of two kinds; the one for 

 letting a part of the fleam efcape, when, on the fire being 

 fuddenly increafed, the fleam becomes fo flrong as to expofe 

 the boiler to the danger of being burft by it; the other for 

 admitting air into the boiler, when, in confeqnence of the 

 diminution of the heat, the fteam in the boiler is condenfed # 

 and a vacuum is formed in it; and when, without this valve, 

 there would be danger, either of having the fides of the boiler 

 crufhed, and forced inwards by the preiiure of the atmofphere 

 from without; or of having the liquid in the containing vef- 

 fels forced upwards into the horizontal fleam conductors, and 

 from thence into the fleam-boiler. This lafl-mentioncd ac- 

 cident, i; cannot happen, unlefs the cocks in fome of 

 the fteam- tubes happen to be open. The two valves eftec- 

 tuaily prevent all accidents. 



The reader will, no doubt, he more difpofecl to pay atten- 

 tion to what has here been advanced, on this interefting fub- 

 jecl, when he is informed that the propofed fcheme has al- 

 ready been executed on a very large fcale, and with complete 

 fuccefs, and that the above details are little more than exact 

 descriptions of what actually exifis. 



A <_»reat mercantile and manufacturing houfe at Leeds, that 

 of MeflVs. Gotl and Co., had the courage, notwithstanding 

 the morfifvt'rig prediction of all their neighbours, and the 

 ridicule with which the fcheme was attempted to be treated, 

 to erect a dyomg-houfe, on a very large fcale indeed, on the 

 principles here defcribed and recommended. 



Oh 



