A way to remove to and fro huge weights with a most inconsiderable strength from place to place. For example, Ten Tunne with ten pounds, and less; the said ten pounds not to fall lower then it makes the ten Tunne to advance or retreat upon a Level.
[A most easie level Draught.] The weight is in this case to be moved “with a most inconsiderable strength.” Ten pounds, or less, are to be capable of moving 22,400 pounds. And the precise conditions are—“the said ten pounds not to fall lower than it makes the ten ton to advance.” The annexed engraving shows, as in No. 25, two cylinders B, C, with their steam-pipe and valve at A, having above a platform G, on which is a loaded truck F, attached by a cord a, at one end passing over a pulley, and the drum wheel D, to the piston B; and a second cord at the other end passing over a pulley at a', attached in like manner to the other piston C. Steam having been admitted to B, on its condensation the piston descending draws along with it the weighted truck F, while the piston C, ascends, drawing in air at E.
We thus attain the strict letter of the conditions set down, the fall and the advance being equal.
28.
A Bridge portable in[1] a Cart with six horses, which in a few hours time may be placed over a River half a mile broad, whereon with much expedition may[2] be transported Horse, Foot and Cannon.
Footnotes
[1]upon a. MS. and P.
[2]there may be.
[A portable Bridge.] The great painter, Leonardo da Vinci, born in 1452, and who died at 67 years of age in 1520, was a man of singularly inventive talent. Among his other projects, he declares:—“I have the means of constructing light bridges, easy of carriage, and equally adapted to pursue or escape an enemy, secure from fire; and as easy to remove as to replace; and also the means of destroying those of the enemy.” See an interesting Memoir of him by J. W. Brown. 12mo. 1828.