Rejoinder to Mr. Quinby on Crank Motion. 97 
true and whole force, leaving friction out of the question, 
with which the piston moves, he declares it equal to the 
whole elastic force of the steam acting upon the piston. 
Mr. Quinby next “takes the liberty to state thatthere is 
notin Messrs. Leans’ reports one word that justifies, or even 
makes admissible, the assertion that there is in the steam- 
engine a loss of power in changing the direction of its action 
from rectilinear to rotary, by the methods in common prac- 
tice! In Tilloch’s Philosophical Magazine we have the 
whole series of reports on the performance of the engines 
used at the mines in Cornwall, by Messrs. T and J. Lean, 
commencing August 1811, and ending November 1818; and 
in these reports the case noticed by the writer of the article 
Steam-engine, Rees’ Cyclopedia, is not mentioned.”? This 
looks like something quite decisive of the question; but 
unfortunately for its bearing upon the case, if is not true. 
Tilloch’s Philosophical Magazine does not contain the whole 
series of repo.ts on the performance of the engines used at 
the mines in Cornwall. The short notices in that magazine 
are professediy nothing more than extracts from Leans’ 
reports. No comment seems necessary on this statement. 
The writer in the Encyclopedia states the cases, as formerly 
quoted by me, with all the circumstances, and declares 
them to be taken from Leans’ reports. Mr. Quinby charges 
him, or me, or both of us, with falsehood almost in so many 
words, because the same facts are not mentioned in a cer- 
tain set of extracts from the same reports.* 
a = 
* As corroborative of the truth of the statement made from Leans’ 
reports, that the rotary motion is not obtained without loss of force, I 
may quote from the report of the committee of the House of Commons, 
made after a long investigation of the subject of steam-boats, the follow~ 
ing passage. ‘ There is also considerable loss in converting the alter- 
nate motion of the piston into the rotary motion of the paddles.” A great 
many authorities might be brought forward upon this subject; but as [ 
Iam not answerable for the truth of Leans’ reports, I have thought it 
not necessary to pursue the subject. 
Regarding the general question of loss, some individuals have no 
doubt believed, as every absurdity finds some believers, that the crank 
‘© occasioned a loss of power,” but it is by no means true, as Mr. Quin- 
by has stated it, that “all the attempts that have been made to apply 
the action of the steam directly to a wheel, or to construct rotary 
engines, have been instituted with the hope, and for the single purpose, 
of obviating the very great loss of power which different individuals 
have supposed to result from the application of the crank.” Indeed 1 
Vor X.—No. 1. 13 
