A. Surface view, with the stone in position.
B. Side view, with the stone in position.
C. Front view of the stone as it rests in the trough against the enlarged centre of the bow-string.
D. Enlarged view of the solid end of the sliding trough. This sketch shows the ball in position against the bow-string; the catch holding the loop of the bow-string, and the pivoted trigger which, when pulled, releases the catch. One of the pair of ratchets which engage the cogs on the sides of the stock, as the trough is drawn back by the windlass to make ready the engine, is also shown. The trough has a keel to it, and slides to or fro along the stock in the same manner as in the arrow-throwing balista. ([Fig. 13], p. 21.)
Compare with [figs. 13], [14], pp. 21, 23, for further explanation of details.
Fig. 17.—A Siege Balista in the form of an immense Stonebow.
From ‘Il Codice Atlantico,’ Leonardo da Vinci, 1445–1520.
Criticism.—A stonebow of vast size. A and B represent two kinds of lock. In A, the catch of the lock over which the loop of the bow-string was hitched, was released by striking down the knob to be seen below the mallet. In B, the catch was set free by means of a lever. C shows the manner of pulling back the bow-string. By turning the spoked wheels, the screw-worm revolved the screwed bar on which the lock A, travelled. The lock, as may be seen, worked to or fro in a slot along the stock of the engine. In the illustration the bow is fully bent and the man indicated is about to discharge the engine. After this was done, the lock was wound back along the screw-bar and the bow-string was hitched over the catch of the lock preparatory to bending the bow again. Besides being a famous painter, Leonardo was distinguished as an inventor and exact writer on mechanics and hydraulics.
‘No artist before his time ever had such comprehensive talents, such profound skill or so discerning a judgment to explore the depths of every art or science to which he applied himself.’—John Gould, Dictionary of Painters, 1839.