of the Steam- E7igi?ies in Corimall. 99 



JefFery and Gribble's engine at Stray Park performed the best 

 duty, being the first that reached 35 millions, and maintain- 

 ing for twelve months an average rate of 32 millions. Woolf 's 

 engine at Wheal Abraham was first reported in October in this 

 year, and performed 34 millions. Number of engines reported, 

 29 ; average duty, 20,534,232." In the early part of 1816, 

 a single engine of 76-inch cylinder was erected at Dolcoath 

 mine by Messrs. Jeffree and Gribble (see preceding note), in 

 place of nn old and defective double one ; which accounts for 

 the diminished consumption of coal which the extract from Mr. 

 Taylor's notice of Dolcoath exhibits. In the same year Mr. 

 Woolf replaced an old engine of 63-inch cylinder, but which 

 had for a short time previously been worked by higher steam 

 than usual, with one of 66-inch cylinder at Huel Abraham : 

 the latter, if I am not mistaken, was set to work about the 

 12th of November. 



I believe I have now satisfactorily shown that Mr. Woolf, 

 instead of being \he frst to introduce the expansive action of 

 steam in one cylinder, was positively preceded several years 

 by Capt. Trevithick, and probably so, a short time, by Messrs. 

 Jeffree and Gribble. Mr. Farey says, " He " (Mr. Woolf) 

 " altered another old engine at Wheal Unity, by adding a 

 small cylinder to it; the performance was improved in about 

 the same degree as that of the old engine with one cylinder *." 

 Perhaps Mr. Farey may not be aware that after being altered 

 the Huel Unity engine did not answer expectation, and the 

 nossels which Mr. Woolf had put in vere thrown out and 

 replaced by others; this only made the matter worse, for the 

 engine would not then keep the water (" in fork'") ; to remedy 

 ihe defect these were removed, and those first put in were re- 

 placed. But, to mend the matter, for several years before the 

 engine was stopped, the use of the small cylinder was dis- 

 pensed with, and the engine worked as a common Watt's 

 single engine ; in which mode it is at present worked on Oppie's 

 shaft in Poldice mine. 



Whilst on the subject of alterations, I may remark that 

 Mr. Woolf had intended adding a small cylinder to the old 

 engine (48-inch cylinder, single) at Huel Vor but the un- 

 toward result of his experiment at Huel Unity, prevented his 

 making the attempt, although a cylinder was purchased for 

 the |)urpose. This was subsequently, after much labour in 

 enlarging the apertures, used by Messrs. Jefiiee and Gribble 

 as cylinder for a small double acting rotatory engine erected 

 to move a staviping apparatus on the same mine, where it is 



• Phil. Mag. and Annals, N.S. vol. vlii. p. WVl. 



O 2 still 



