214 HORSK-POWERS OP A STEAM-EVCrNE. 



XVII. 



Familiar Account of the Method of ejlimating the Value qf a 

 Steam-Engine in Horfe-Povcers as they are called. By a CorrC" 

 fpondent. 



To Mr. NICHOLSON. 

 SIR, 



Introduaory l\s your excellent Journal is the repofitory for ufeful informa- 

 letter. tion, whether fcientific oVpra6lical,I have thought I (hould oblige 



many manufacturers and others of your readers, by fending you a 

 very clear report about horfe-powers, which a friend of mine 

 has communicated to me, and was received by him from an 

 eminent character in anfwer to an enquiry profeffionally made. 

 It clearly appears from this paper, that the calculation by 

 horfe-powers muft be fallacious, unlefs engineers could agree as 

 to the quantity of work they would arbitrarily, in the firft 

 inftance, afcribe to one horfe; and then theexpreffion would be 

 nugatory. And not only fo, but it would not then be true that 

 the value of a fleam-engine in work, however clearly expretT- 

 ed in quantity per day, would be fairly fhewn, unlefs the 

 •wages or food of the working being were taken into the ac- 

 count. Coals may be fliled the food of a fteam-engine, and no- 

 thing is more evident than that, if two engines raife equal quanti- 

 ties of water j5er hour, but confume different quantities of coal, 

 they will not be equally beneficial to the proprietors. I would 

 therefore propofe, that the eftimate fliould be made by attend- 

 ing to thefe two particulars only, and faying nothing about 

 hortes, at leaft in fpecific arguments intended to have legal 

 efFecls : And, as a fupplement to the fa6ls and obfervations 

 contained in the report, I will add, that one of the beft en- 

 gines of Boulton and Watt, has been known to raife between 

 28 and 30 millions of pounds of water to the height of one 

 foot with one bulhel of good coals, which appears to be an 

 outfide meafure ; and that, though there are fubfequent im- 

 provements both in the con(lru6lion of furnaces and the work- 

 ing gear, yet there are Ibme among late engines which fall 

 fliortof 20 millions. 



I am. Sir, 



Your conftant reader, 



E.T. 



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