Experiments on Water Rebounding in a Level Channel
A glass-sided channel with marker particles for watching how water leaps and scours
Leonardo sets out an experiment on the leaps of water over a level channel. He instructs the maker to build a channel with one side of glass and the rest of wood, and to mix millet or paper-maker's paste into the water so its currents show up clearly through the glass; then to line the bed with sand and fine gravel, flatten it, and watch where the leaping water lifts material or lays it down. A marginal note relates the up-and-down motion seen here to the side-to-side motion of water beating against its banks. The drawing shows the trough in perspective with wavy flow lines running along it.
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Glass-sided channel with millet or paper pulp to reveal the current
One side of the channel is to be glass and the rest wood, and the striking water mixed with millet or paper-maker's paste so its motions are visible. After observing the leaps, the bed is filled with sand and fine gravel, flattened, and the water made to leap on it to see where it erodes or deposits. The bank toward the wood is then built of clay and its effects watched through the glass in a continuous flow.
Vertical leaps stand for lateral impacts against the banks
A marginal note observes that what the water is seen to do between up and down here, it will also do between one side and the other when it beats against the banks. The one exception is the water that, leaping, folds back upon itself.