been made in the Petforma7ice of Sleain-Engines hi Cornwall. 423 



worked on Mr.Woolf's system (that is, by high pressure steam 

 acting expansively), are found better for draining deep mines, 

 than Those with two cyhnders. Mr. Woolf 's engines with two 

 cyhnders, for turning machinery, continue in use in London, 

 and are very common in France ; they execute their work with 

 less fuel than any engines used for turning machinery. 



It is asserted at p. 39A, that variation in the elasticity of the 

 steam employed by no means affects the invention, meaning 

 Mr. Watt's invention of expansive working ; also that evidence 

 seems to preponderate against the use of steam of very high 

 tension. And yet the cokmm there entided Highest of Watt's^ 

 beginning with 40-6 millions in 1823, and ending with 79- mil- 

 lions in 1829, relates solely to engines which are worked on 

 Mr. Woolf's system ; that is, by high pressure steam acting 

 expansively. Let it be shown when and where any engines, 

 not strictly within the meaning of those words, ever raised any 

 thing like 40-6 millions, which is the least in the column en- 

 titled Highest of Watt's; or when and where Mr. Watt ever 

 worked, or proposed to work, his engines by high pressure 

 steam acting expansively. 



Mr. Watt's engines are said at p. 324 to have done about 

 25 millions average duty, whilst superintended by his own 

 agents. All the watei'-works in London are now served by 

 Mr. Watt's engines, made by his successors in business at Soho, 

 and good specimens of execution : they are worked by low 

 pressure steam, acting expansively in one cylinder, and the 

 performance of the best of them is about 25 millions ; hence 

 no improvement has been made in the performance of what 

 are really Mr. Watt's engines since his time. 



Notwithstanding this, your correspondent has put the title 

 Highest of Watt's, to performances increasing each year from 

 40-6 to 79' millions, without explaining to your readers how 

 such a great increase has been effected in the performance of 

 what he calls Watt's engines. Any explanation that could have 

 been given, must have brought out the fact which is kept back, 

 viz. that they are worked by high pressure steam acting ex- 

 pansively in one cylinder; a system which Mr. Watt never did 

 propose or execute ; but as Mr. Woolf did both propose and 

 execute it, and brought it into common use in Cornwall, how 

 can my evidence, that those engines are on Mr. Woolf's sy- 

 stem, be objected to? Or with what propriety can they still be 

 called Watt's engines, when they are worked on such a dif- 

 ferent system as higii pressure steam, and low pressure steam, 

 and with such a very great advantage in cost of iucl, beyond 

 all that Mr. Watt ever did accomplish ? 



If variation in the elasticity of steam no way affects the in- 

 vention 



