HISTORY OF THE INVENTION. 
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cranked. In the following description the same letters of reference indicate similar 
parts. A A are the cylinders, which are of 37 inches diameter, and have a 
stroke of 3 feet; B B are the piston rods; C C the cross heads; D D the side 
rods, the lower ends of which work in guides fixed to the sides of the cylinders; 
E E are the connecting rod side rods, which form in fact part of the connecting 
rod; F F are the connecting rod cross heads; and G G are the connecting rods. 
H H are the cranks, which are placed at a right angle to each other. I is the 
intermediate shaft, which is cranked at J to work the air pump; and K K are 
the eccentrics for moving the slide valves L L. The crank for working the 
air pump is placed opposite the two engine cranks, as in the 
margin, in order that by causing the air pump to make its 
ascending stroke when the pistons of the engines are descend 
ing, the weights may in some degree counterbalance each 
other. M is the condenser, and N the hot well; 0 O are 
the feed pumps, which are worked by arms extending from 
the air pump cross head P, the ends of which work in 
guides Q Q. 
RR is the spur wheel framing. The wheel S is affixed on the engine axis; 
the cogs are of horn beam; these work into the pinion T. Upon the same axis 
as the pinion T is affixed the cog wheel U, which is of the same pitch and 
diameter as the wheel S. The wheel U communicates its motion to another 
pinion V (of the same dimensions as T), which is affixed on the propeller shaft 
W W. The effect of these wheels and pinions is to produce an increase in 
the velocity of the propeller shaft in the proportion of 5*33 : 1, so that, when 
the engine shaft makes 25 revolutions, the propeller shaft makes 133*3 revolutions; 
the latter are supported on bearings X X, and united at Y Y by a peculiar 
coupling shown in the diagram 
a a are the ends of the shafts to be coupled, which each form the half of 
a solid cylinder, such as would be produced by dividing it longitudinally in 
equal portions. When these ends are placed together with their flat surfaces 
in contact, the coupling box b is slid over them, and a key is driven into a