upon one of the spokes of the engine wheels; the connecting rod fixed to the cross beam of the engine, and moving with the piston, being attached, at the lower end, to the spoke of the wheel, and working in a ball and socket joint. The reciprocating motion of the piston was thus

converted, by the pin acting as a crank, into a rotatory motion.

Fig. 51.

Fig. 50. page 223. represents the side, and fig. 51. the end elevation of this engine; a, b, c, d are the connecting rods, attached at their lower

ends, b, c, to the pin fixed on the spokes of the wheels A B.

The

To keep the cranks at right angles with each other, the patentees used a kind of endless chain, consisting of one broad and two narrow links, which lay upon or passed over a toothed wheel, fixed to each axle, as shown in the figure. principle of action of this was very similar to the plan proposed of giving motion to the wheels of carriages by Messrs. Tindall and Bottomly. The periphery of the wheels fixed on the axles being furnished with cogs or teeth, projecting about an inch, these teeth entered between the two narrow links, and had a broad link between every two cogs, resting on the rim of the wheel, which caused the chain to move round with the wheel, and prevented one wheel being moved without the other.

Mr. G. Stephenson may be considered to be the first who successfully used locomotive engines. It has, indeed, been stated that he had remarked, in 1814, that if the wheels of carriages could be made to have sufficient adhesion on the rails, there was no limit to the speed such an engine could go at, provided the works could be made to bear the action. This opinion has, indeed, been corroborated by the events of subsequent years;

but the locomotive engine had a long course of probation to undergo before it reached any degree of perfection.

LOSH AND STEPHENSON'S PATENT.

The next attempt at improvement on it which Mr. Stephenson made was part of Messrs. Losh and Stephenson's patent in 1816. The improvement they aimed at is distinctly stated in the specification of their patent to be, "sustaining the weight, or a proportion of the weight of the engine upon pistons, movable within the cylinders, into which the steam or water of the boiler is allowed to enter, in order to press upon such pistons, and which pistons are, by the intervention of certain levers and connecting rods, or by any other effective contrivance, made to bear upon the axles of the wheels of the carriage upon which the engine rests."

Fig. 50. page 223. e e e show the cylinders placed within the boiler, one side being supposed removed to expose them to view: ggg are solid pistons, fitting the interior of the cylinders, and packed in the usual way. The cylinders are open at the bottom, and were screwed upon the frame of the

engine. The piston was furnished with an inverted rod, the lower end of which passed through a hole in the frame, and supported the engine, and pressed upon the chair which rested on the axis of the wheels upon which the carriage moved. The chair had motion up and down with the piston rod. The pressure of the steam upon the piston transmitted the weight to the axle, and the reaction took an equal weight from the engine. Supposing the area of the cylinders and pressure on the piston to be equal to the weight of the engine, the latter would be supported, as it were, by the steam, thus making the steam serve the purpose of an elastic spring. When four wheels were used the weight was equally divided upon them; but when six wheels were used, as shown in the figure, only one frame was required for the carriage, which simplified the construction. This invention, like many others, aimed at too much, was too complicated, and not sufficiently precise to be of much use.