100 Ward's Steam-Engine. 
circle of motion. The force BD, in this case, is resolvable 
into BH and HD. parallel and perpendicular respectively to 
the radius AD ; and that part of it, which is exerted in the 
direction of the tangent, will be represented by HD. 
These two tangential forces EB and HD, are to each othi- 
er inversely as their distances from the common centre of 
motion A. For, in the two triangles, ACD and AFB, the 
angle at A is common ; and the angles AFB and ACD be- 
ing right angles, the remaining angles ABF and ADC are 
equal, and the two triangles similar. Therefore, BF (or 
HD) : DC (or EB): : AB: AD. And inversely, HD : 
AB:: EB: AD. 
But, from the properties of the Lever, forces which are 
to each other inversely as their distances from the fulcrum, 
or common centre of motion, counteract each other, and 
produce an equilibrium. The two forces, HD and EB, 
therefore, would counteract each, other, or, which is the 
same thing, produce equal effects. 
The error on this subject has arisen from supposing an en- 
gine to operate upon the larger circle LDM, from without 
its circumference, when, of course, the sweep of piston 
would be equal to the diameter of the circle LDM ; and 
then comparing this engine with one on my plan, fixed at 
B, and with a sweep of piston, equal only to the diameter of 
the small circle BKZ. ‘Taking it for granted, that both en- 
gines would be of equal power, it was easy to show, that the 
one on my plan would loose as much more power than the 
other, as the diameter of the large circle was greater than 
that of the less; but it was overlooked, that the two engines 
would consume steam and fuel exactly in the same propor- 
tion,—that my engine would consume as much less steam 
and fuel as its sweep of piston was less than that of the 
other,—that, in a word, the power consumed by my engine 
would be equal only to AB, while that consumed by the 
other would equal AD. 
The advantages of my engine over the Lever Engine, 
may be enumerated as follows: 1. The alternate transfer 
of momentum from the reciprocating mass to the fly-wheel, 
and vice versa, as above described, occasions a strain upon 
those parts of the engine, which connect the alternating with 
the rotary parts ; and this strain increases exactly in pro- 
portion as the time, in which it takes place, decreases ; for, 
