a Reply to Mr. Quinby on Crank Motion. 
refer to the authority by which they were made out. 
“It must, however, be concluded, that a very great bl 
any loss whatever of the acting power 
Before Mr. Quinby — that a very great blunder 
was made in these estimates, it would have been well for 
him to have hantéed up some icant on the subject. 
if he had consulted so common a book as Rees’ Cyclo- | 
article Stean-Engine, he would have found the fol. > 
‘statement: “ By agreement of a number of respect- 
oprietors of tin and copper mines in Cornwall, who 
2d to have ascertained the real work their respective 
steam engines were a &c.—“ it was agreed that 
a counter should be attached to each engine, and all the 
engines put under the 
and competent engineer, “who pers: report, , monthly, ri 
following particulars.” Then, amongst other particulars 
enumerated, “ Pounds, lifted one foot high, by’a bushel of 
coals.” 
“ Messrs. Thomas and John Lean were appointed to the ¥ 
general superintendence, and since thattime they have pub 1 
lished monthly reports, &c.”” By these reports, it a3 
that two large ene used for pumping, raise on an aver- 
age about 50, 0 pounds one foot high, foreach 
el of coals consumed; and one of them raised, fe 
month, 56,000,000 nds: again, says the sa 
“ Before quitting the subject of double engines, emp 
to give a rotative motion to machinery by a crank, we must 
notice a remarkable difference, shewn by Messrs "Lean’s 
reports, between the performance of the small — ene 
ut mH 
ployed | in drawing the matter out of the mines, and those 
n pumping water.” 
* *€We should think th ss of power from ction i in 
avg up buckets ie would not be greater that 
he friction of the and of the ' or movine 
be a 
ipes 5 asl er, all the difference mt io se eell- 
to the application of the rotative motion, and 
