(221.)

Mr. Francis Humphrys has obtained a patent for a form of marine engine, by which some simplification of the machinery is attained, and the same power comprised within more limited dimensions. In this engine there is attached to the piston of the cylinder, instead of a piston-rod, a hollow casing D D ( fig. 130.), which moves through a stuffing-box G, constructed in a manner similar to the stuffing-box of a piston-rod. In the figure, this casing is presented in section, but [Pg471] its form is that of a long narrow slit, or opening, rounded at either end as exhibited in the plan (fig. 131) of the cylinder-cover. The crank C is driven by the other end of the connecting rod H, the crank-shaft being immediately above the centre of the piston and the connecting rod passing through the oblong opening D, and descending into the hollow piston-rod it is attached to an axis I at the bottom of the piston. A box or cover K K encloses the cross-piece or axis I with its bearings, and is [Pg472] attached so as to be steam-tight to the bottom of the piston. A hollow space L L is cast in the bottom of the cylinder for the reception of the box K K, when the piston is at the bottom of the cylinder.

Fig. 130.

Fig. 131.

By this arrangement the force by which the piston is driven in its ascent and descent is communicated to the connecting rod, not, as usual, through the intervention of a piston-rod, but directly from the piston itself by the cross-pin I, and from thence to the crank C, which it drives without the intervention of beams, cross-heads, or any similar appendage.

The slide-valves regulating the admission and eduction of steam are represented at a; the rod of the air-pump is shown at d, being worked by a crank placed on the centre of the great crank shaft.[38]