A Self-Refilling Water Clock of Twenty-Four Vessels
Vases of the hours driven by bladders and levers, with studies of rising floats and falling water.
The central column and great figure describe a water clock built from cylindrical clay vessels, the 'vases of the hours', in which internal bladders and a saddle-released iron trip successive vessels so that a float rises, strikes levers, and redirects the flow through twenty-four basins over a full day. Flanking studies examine the physics of water: whether a submerged bladder rises faster in wide or narrow, deep or shallow water, and how a jet falling into standing water penetrates and surges back in an oval bubble. Leonardo specifies that the tubes be of fine clay fired to vitrification, and claims the device runs perpetually, needing less adjustment the more it works.
On this page
How fast a submerged bladder rises
Leonardo poses whether a bladder (otre) held at equal depth rises faster in a wide expanse of water than in a narrow one, and whether it rises faster in greater or lesser depth. He answers that it rises faster in wide water, since a channel could be so narrow that the bladder would make no headway at all.
Water falling into water and the oval bubble
Water that falls in a perpendicular line into flowing water makes a curved penetration and a curved surging. The crest of the part that rises into the air will not lie in the middle of the base of the resulting bubble, and that base is oval.
Vitrified clay tubes b c d - a
The central cylindrical vessels are lettered b c d - a. These pipes are to be of fine clay, fired so thoroughly that they reach the point of vitrification, giving them a hard, watertight body for the clock.
The vases of the hours and their bladders
In the group of three vessels, the 'vases of the hours' open in sequence: the first opens, then the water of the second passes through the first, and so on. Leonardo notes that something must close them again, and that this closing is done by the bladder (baga) each vessel carries within its body.
The twenty-four-hour trip mechanism m, K h, v r, o p
When vessel m has filled the vessel beneath it, bladder b rises and the saddle releases the iron v r, so the lower bladder K h rises to S d until v r overcomes the device a b; K h then rises from S d to o p in a full turn, striking lever f with r and lever t with v. Vessel m then pours into all twenty-three other vases; when full, the overflow strikes at e, turns m aside, and only when the twenty-four hours are sounded does the last basin empty, striking q and setting m to pour again into t g, so the cycle repeats forever.