Reply to Mr. Quinby on Crank Motion. 281 
ness of the engines. These are usually fourteen, sixteen, 
and twenty-four inches in diameter; but their performance 
with respect to coals is only three, three and three quarters, 
four, and five millions. ‘The best engine they have, draws 
only from nine and a half to eleven million pounds one foot 
high for each bushel of coals; which is only one third of 
the product of the best large engines, employed in pump- 
ing. | | 
“One of Woolf’s double engines at Wheel Fortune 
mine, in May 1816, drew only three million pounds one 
foot high, with each bushel ; but another at Wheel Fortune 
mine drew six millions. 
Taking from the preceding statement two facts, and those 
not the most favourable to the account given in the Review, 
and comparing the highest performance of the rotary en- 
gine with the best pumping engine: viz. 11,000,000 with 
56,000,000, gives the performances as 1 to 5.09, a differ- 
ence even greater than is stated in the Review. 
Now it is asked, does Mr. Quinby suppose that his de- 
monstrating what the writer of the Review never for a mo- 
ment doubted, that motion may be communicated by a 
crank without loss of force; is to put downa long series of 
facts so carefully ascertained as those reported by the 
Messrs. Leans? It is submitted for any unperverted mind 
to judge, whether the paragraph in the Review is not a fair, 
and, on the whole, a narrow statement of the loss, ‘“‘ as ap- 
pears from the reports on the performance of the engines 
used at the mines in Cornwall.”’ 
Mr. Quinby favors us with his opinion that the frequent 
altempts to make a rotary engine are “‘ unnecessary and 
idle.” No notice would have been taken of this upinion 
was it not connected with a sentence of the Review, ina 
manner by which it may be supposed that the author of the 
Review appreciates these attempts more highly than they 
deserve. But this is by no means the case. A plain reia- 
tion of attempts to accomplish a particular object is made, 
and the unsuccessful result of those attempts is as plainly 
stated. ‘This was certainly within the professed object of 
the article in the Review, and appeared to the writer a ne- 
cessary relation. 
It may be observed, however, that it is not for Mr. 
Quinby to set bounds to the efforts of invention. [tis the 
Vor, VILT.—No. 2. 36 
