The adjoining cut is explanatory of a direct-action engine invented by Mr. Parkyn, which resembles the preceding in the circumstance of the piston-rod serving also as the connecting rod, but by a somewhat different disposition. a is the rod which serves at once the purpose of the ordinary piston rod and connecting rod, being attached at the lower end to the piston b, and at the upper to the crank pin c; d is a recess in the piston b, for the reception of the lower end of the rod a; e a cross pin passed through the body of the piston b, and the eye-hole f, in the lower end of the rod a, turning freely upon the pin. The motion of the crank and connecting rod a being angular and variable, while the piston b moves uniformly in one vertical plane, in order to bring the two motions into harmony with each other, the following arrangement is adopted. In the centre of the cylinder cover g, and in a line parallel with the crank, there is an elongated slit, h; and immediately over this there is a supplementary steam-tight cover i, which moves backwards and forwards at right angles to the main shaft, in conformity with the varying positions of the crank and connecting rod a, much in the same way as in a lathe the tool carriage of a slide-rest moves on its bed.
The under portion of the stuffing-box has two arms or pins, which turn in suitable bearings in the upper or supplementary cover i, whereby the stuffing-box is enabled to adapt itself to the line of the piston and connecting rod throughout the entire revolution of the crank. ,