Sullivan on the Revolving Engine... 8 
some part of the force, was undoubtedly lost at every stroke, 
in giving motion to the balance w eel necessary to equalize 
the movement. Whether the ions of force by a-crank is 
actual or theoretical, may be a question. It is not one how- 
ever which applies to this engine so much as to others, be- 
~~ it is moved by very elastic steam always ig 
or both of the two cylinders which comp 
a 
Your correspondent deems this unimportant to ake ques- 
tion he raises,—which may answer more hy to 
— readers, od a — in point, from Dr. Young’s Lec- 
gressive motion of is rod will be ae accelerated and 
retarded, and for a considerable space of the revolution 
force exerted will be nearly uniform ; but if we dhompt to 
communicate at once to the rod its whole velocity in. each 
direction, as has sometimes been done, the motion would 
become extremely oe and the machinery would sa 
destroyed by the st 
* On the other hand it must be observed, that force ap- 
plied to the machinery, may in general be divided into two 
forces ; the one employed in opposing the force, so as to 
produce an equilibrium only, and the other in generating 
momentum. 
e With respect to the first portion, a single crank has the 
inconvenience of changing continually the mechanical ad- 
vantage of the machine; with respect to the second, its 
motion in the second quarter of its revolution is accelerated, 
instead of being retarded by the inertia, w which this portion 
of the force is intended to overcome ; and from the combi- 
nation of these causes, the motion must necessarily be ren- 
dered ve ener 
s may however be poms & removed by em- 
slope hart cranks in pairs, one ley m being fixed so 
as to sig aright angle with the o 
Here Dr. Young does not seem is or this supposable 
decision of force ‘ lost to all useful purposes,” but incident to 
the nature of machinery—or remediable on the same prin- 
ciple by which ste as a power, is applied by the double 
revolving engine. Ww) 
vatever deduction is to be made then _ 
acc : 
