This arrangement of marine engines, shown in the opposite engraving, originated, we believe, with Mr. Penn, of Greenwich, who has applied it to some steam-boats on the Thames. At a is the cylinder; b the piston-rod, carrying the cross-head c c; this cross-head consists of four arms, branching diagonally from the centre. On each side two side-rods d d are suspended from the extremities of the arms c c of the cross-head, and are attached at the lower end to a bar e. In the centre of this bar is a pinf, to which the forked end g of the connecting-rod h is coupled; i i are two guide-rods, upon which the bar e slides, the rods passing through brass bushes attached to the side of the bar; k is the crank, and m the side-frame; n the slide-case, andp the steam-pipe.

When only one engine is employed, instead of a forked connecting-rod the rods g are sometimes connected directly to the crank, the pin of which is equal in length to the distance between the two connecting rods g. By this means a longer stroke may be obtained in the same height, and the connecting rod is somewhat lighter.

Perm s Direct Action Engine 546