Mr. J. Taylor on Rotatory Steam Engines. 137 
Thomas seem further to prove that which I merely wished 
to draw the attention of engineers to, and by making it public 
in your pages, to give information which otherwise might not 
for a long time to come have reached to other districts. 
Having observed a certain instance of great improvement 
in the ceconomy of fuel, applicable to that kind of engine which 
is mostly employed in all the varied operations of our numer- 
ous manufactures, I merely desired to communicate the know- 
ledge of the fact; and, as I expressed in my letter, I pointed 
it out as deserving attention and inquiry. I think it much 
more important to the public to consider the steps by which 
improvements are worked out to practical advantage than to 
indulge in disputes about such originators of an invention as 
did little more than to broach an idea, good enough, perhaps, 
in itself, but which may only have been rendered valuable by 
the superior skill or industry of others exerted in bringing it 
into useful and general application. 
This observation may apply to what Mr. Henwood chooses 
to say of Mr. Woolf, respecting whom he seems to lose no 
opportunity of endeavouring to detract from the merit to which 
I and many others think he is entitled; my expression was 
that we owe to him the method of working high-pressure 
steam expansively *, and this is still my opinion. I have in 
another place recorded Captain Trevithick’s engine at Wheal 
Prosper, and so far have done him justice, but this engine 
did only about 26 millions duty, and did not equal other en- 
gines then working in the common way; nor does it appear 
that Captain Trevithick followed up his invention or produced 
any improvement upon the duty of the engines in Cornwall, 
the average not having increased until two years afterwards, 
when some of Mr. Woolf’s engines had attained to a duty of 
50 millions, and Messrs. Jeffrey and Gribble had successfully 
adapted the same principle to an engine with one cylinder. 
Mr. Henwood in a note states correctly that Captain Lean 
reports the duty of the Charles Town engine at 40 millions, 
and not at 60, as stated by me. What, however, I did state 
was, that when [I saw it, soon after it was put to work, it was 
calculated to be performing a duty of about 60 millions. This 
calculation was made by the principal agent of the mine, and 
the engineer on the spot, and I saw no reason to doubt their 
accuracy, and gave their account as I received it, adding, how-. 
ever, that I had desired that its performance should be re- 
gularly reported in the monthly duty papers, by which of 
course any error in this respect would certainly be set right ; 
{* Our much respected predecessor, Dr, Tilloch, expended a consider- 
able part of his property in his zeal for assisting Mr. Woolf.—Ebrr.} 
Third Series. Vol. 8. No. 45. Feb. 1836. Q 
