ae 
318 A. B. Quinby on Crank Motion. 
; Review, he did believe that the crank occasions a loss of 
hee -fourths of tlie whole power employe 
here is,” says this writer, ‘in the steam- engine, a loss 
wer in changing the direction of its action from rectili- 
near to rotary, by the mtehods in common practice,” &c.; whic 
on an average amounts to about three-fourths of the whole 
power, as appears from the reports on the ae ose of the 
engines used at the mines in Cornwall.” 
ow it-is ceftainly not difficult, for any person who can 
comprehend plain language, to understand what is ex- 
pressed in the above quoted sentence. ‘There is, in the 
steam-engine, a loss of power, in changing the direction of tts 
action from rectilinear to rotary, by the methods in common 
practice.” Can any words convey a ‘clearer or more definite 
meaning than these here used :—for does not every individual, 
who has the least knowledge on the subject of the construc- 
tion of the steam-engine, know thaf “the method in common 
ractice,” for changing the direction of the power from rec- 
tilinear to rotary, is the crank? And yet the writer of the 
article in question boldly asks, “Can any one pretend, for 
one moment, that there is any thing in this paragraph whic 
arrants Mr. Quinby’s assertion that the loss of power is sup- 
posed to result from the erank 2?” 
re is something more conclusive to be said on this 
subject. In Rees’ Cyclopedia, article steam-engine, we hav 
the following words: “ Before quitting the subject of double 
engines,* [double cylinder engines | employed to give a rota- 
tive motion to machinery by a crank, we must notice the re- 
markable difference, shown by Messrs. Leans’ reports, be- 
tween the performance of the small engines employed in 
drawing - a, out of the mines, and those used in 
pomp ing w 
Saboald think the loss of power from friction, in draw- 
ing up pilkess by a rope, could not be greater than the fric- 
tion of pump-buckets, and of the water moving in the pipes; 
therefore, all the difference must be attributed ce the applica- 
tion of the rotative motion, [by the crank,] and to the small- 
ness of the engines ; these are usually 14, 16, and 24 inches 
* Those who are familiar with the construction of — aoa 
engines, will re by reading the article steam-eng 
meant is ee *s Scania: epinaas oa 
_ Cyclopedia, tt engine here 
gine, and not the double engine invented by Wat 
/ 
