Ward’s Steam-Engine. 97 
ing accelerated during one half of the revolution, and retard- 
ed during the other half; but its revolving motion is con- 
tinual, moving always the same way. ‘The celerity of its 
revolution, or velocity of its angular motion, regularly and 
alternately increases, during one half of its revolution, and 
falls off just as much, during the other half : but, for reasons 
similar to that, which | gave above, this operation is at- 
tended with no disadvantage; for the momentum, which 
the cylinder, during its acceleration, receives from the 
wheel, it returns again to the wheel, during its retardation ; 
so that it accelerates the wheel as much, during its own re- 
tardation, as itretarded the wheel, during its own accele- 
ration. It is this peculiarity of motion in the cylinder, 
(namely, its regular and alternate acceleration and retarda- 
uon,) which induced me to distinguish my Engine by the 
name of The Alternating Steam-Engine. 
To dispense with the fly-wheel, it was long ago sugges- 
ted, that, if two cranks were used in such a way as that one 
should be at its greatest action, while the other was at the 
dead-point, the motion would be very nearly regular; and 
Mr. Brunel, in England, constructed, not many years since, 
an engine upon this plan, having two cylinders, which acted 
on two cranks at right angles to each other on the same 
axis. In my engine the same thing is done, by having two 
eylinders, whichact upon two cross-pieces at right angles to 
each other. ‘The cylinders are suspended side by side in 
the water-wheel, between the same two centre-pieces, their 
contiguous sides having, the one a box, the other a gudgeon 
inserted in the box : and they are further supported by a 
bridge, extending from the ends of each around the other, 
embracing the opposite gudgeon. The cocks are placed on 
the outsides of the cylinders in the manner above describ- 
ed ; the steam being conducted to and from each cylinder, 
through each centre-piece. 
It will be seen, at a glance, that my engine,—like all 
others, that have been turned to any account in practice,— 
acts upon the principle of the crank; or, in more general 
terms, upon the principle of a perpetually varying lever. In 
addition to the supposed loss of power, arising from the re- 
ciprocating movement, it has long been the settled doctrine, 
that the crank is also chargeable with another disadvantage, 
in consequence of this perpetual variation in its leverage. 
Vor. tV.....No. 1. 13 
