BETWEEN the two bo ats, A and B, which are firlllly attached to each other by beallls, U, is placed the large wheel, J), provided with paudles on the periphery, in order that the current of the river may cause it to reo volve, and with a crank shaft at the part E. Upon these boats is erected the frame of the pile driver, which differs from the ones in ord inary use only in being provided with the wheel, F, and the drum, G, both of which ha ve one axle, H, in cOlllmon. As regards the ropes of

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... s machine, the one, 1. th at supports the III on key, 0, has a hook, K, at one end, passes over the pulleys, L and M, and winds around the wheel, F; and the rupe, N, beiug wound at one of its extremities around the druw, G, is at tached throu gh the other to the crank, E, of the axle of the large wh eel, J). 'fhis machine is so arranged that when it is desired to use it, and the river curre nt causes the wheel, J), to revolve, the crank, E, of its axle follows its motion. In the circle that it describes in descending from its highest to its lo west point, it pulls the rope, N, and consequently causes the drum, (J-, and the wheel, F, to revolve, and, in making such motion, winds the rop e, L around its circumference and causes the monkev, 0, to ascend. As soon as the monkey has reached the necessary height, the hook, K, is freed, as we shall explain, and the monkey, in rapidly falling, produces its useful effect upon the pile that it is to drive. After baving seeu the Illaneuver made by the crank, E, in descend ing, it is necessary to explain that when it rises fro m the lo west point of the ci rcle that it describes up to its highest poin t of elevation, it slackens the rope, N, and, as the hook, K, is loaded with a block of lead and is no longer drawn upward, it descends by its own weight, and, thereby causing the rope, I, to unwind from the wheel, F, makes the rope, N, wind around the drullJ .