OF RAIL-ROADS.

141

the end a attached to the cross-beam, and the end b to oneof the spokes of the wheel; in like manner the end d of theconnecting rod c d, is attached to the beam of the otherpiston, and h and c to a pin fixed in the spokes of thewheel B. By these means, the reciprocating motion of thepiston and connecting rod is converted by the pin uponthe spokes acting as a crank into a rotatory motion, and thecontinuation of this motion secured by the one pin or crankbeing kept at right angles to the other, as shewn in thedrawing.

To effect this, the patentees had two methods,to crank the axle on which each of the wheelswere fixed, with a connecting coat between,to keep them always at the angle, with re-spect to each other; or to use a peculiar sortof endless chain, passing over a toothed wheel,Fig. V. on each axle. This endless chain,which is now solely used upon these kind ofengines, consisted at first of one broad and twonarrow links, alternately, fastened together atthe ends with bolts ; the two narrow links werealways on the outside of the broad link; con-sequently, the distance they were separatedlaterally would be equal to the breadth of thebroad link, which was generally about twoinches, and their length three inches. Theperiphery of the wheels, fixed upon the axlesof the engine, were furnished with cogs, pro-jecting from the rim of the wheels, (otherwiseperfectly circular and flat) about an inch or