Fig. 3392a.
2. The addition to each high pressure cylinder of a low pressure cylinder constitutes a compound engine, and if the engine has also a condenser, it is a compound condensing engine, an example being shown in [Fig. 3392a], which represents an engine in which the link motions are employed to vary the points of cut off of both cylinders, as well as to reverse the engine. The engine being small, the power required to move the links is small enough to permit of their operation by hand, by means of the hand lever l, which is secured to its adjusted position on the sector t by the small lever nut shown on the side of the lever. The lever l operates a shaft d which shifts both link motions. The air and circulating pumps are at the back of the condenser, being operated from the beams b, b, each beam connecting to rods j which connect to rod c, which drives the air and circulating pumps.
The steam from the high pressure cylinder exhausts into a receiver or chamber between the two cylinders, and from which the low pressure cylinder receives its steam.
The exhaust from the low pressure cylinder passes into the condenser, where it is condensed, leaving a partial vacuum on the exhaust side of the low pressure piston.
| VOL. II. | COMPOUND MARINE ENGINE. | PLATE XXXVI. | |||
| Large image [Fig. 3393] (124 kB), [Fig. 3394] (147 kB).  |  | ||||
| Fig. 3393. | Fig. 3394. | ||||
![[Fig. 3393]](#8656825660018214284_large1006a.png.id-3999547634519286667.wrap-0.html.html){kind=link}
![[Fig. 3394]](#8656825660018214284_large1006b.png.id-247626573369825759.wrap-0.html.html){kind=link}
[Figs. 3393] and [3394] show the arrangement of the pumps on a pair of compound engines for a dredger. The steam from the low pressure cylinder passes into the body of the condenser with which the air pump is in communication, as shown in the end elevation. At a is the foot valve of the condenser. The piston of the air pump has a similar valve, and at e is the delivery valve.
The circulating pump is shown in the back elevation ([Fig. 3394]), being a piston pump which forces the water through the tubes of the condenser.
There are two principal methods of compounding, in one of which the two cylinders are placed one above the other, with their axes in line, and both pistons connecting to the same crank, while in the other the cylinders are side by side, and each connects to its own crank, the two cranks usually being at a right angle.