OF RAIL-ROADS.

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diameter, and two feet stroke ; the boiler wascircular, eight feet long, and thirty-four inchesdiameter; the tube twenty inches diameter,passing through the boiler.

Fig. III. Plate IV. -will shew the manner by which thepower of the engine was communicated to the wheels, andthe loco-motion effected. A A are the wheels of the carriagesupporting the engine; B B, the frame of the carriage onwhich the boiler is fixed; a b and c d are the connectingrods, similar to b c be. Fig. I., transferring the motion fromthe piston to the crank, b. c. and df are the cranks whichturn the two small cog-wheels e f; the cranks are placed insuch a position, with respect to each other, that when oneof them is perpendicular, or in a line with the connectingrod, the other is horizontal, and at right angles to it; andthis arrangement is continually secured by the interpositionof another cog-wheel, of the same size, and working intothe other cog-wheels, e and f

Two larger cog-wheels, K and K, are fixed upon the axlescf the carriage-wheels, which, when the small wheels e and_/are turned round, by the rotatory motion of the crank, arealso turned round, and with them the wheels of the engine.

The wheels of the engine being thus turnedround upon their axis, the friction of the rimof the wheels against the rails being regulatedby the pressure upon them, and preventing thewheels from turning or sliding round upon therail, would necessarily cause them to roll for-wards along the rail, and thus produce a pro-gressive motion in the engine.

If the power required to produce, or the