Water eddies for scouring and reclaiming a canal
A rebounding eddy that bores deep, a dead pool that silts up, and reclaiming a marsh.
Continuing the study of eddies in Notebook F, this page turns their behaviour to practical canal work. A diagram (o, c, a, b) shows an eddy of 'double power' that strikes the bank, leaps into the air and falls back, boring a sudden deep hollow in the bed and carrying off soil, the most powerful means of scouring depth, especially when the water is turbid. A second diagram (a, f, m, n, b) shows the opposite case, where a current dying in a 'dead pool' drops its sediment and raises the bottom. Marginal notes cross-refer to a method for emptying a canal and praise the benefit of silting up a marsh to purge the air and win workable land.
On this page
A rebounding eddy that bores deep into a bed
Let o c n be the current; a is an eddy of double power, for besides its revolution it strikes the bank, leaps into the air and falls back onto the water, penetrating, striking and hollowing the bottom with sudden depth. To the percussion is added a boring from the revolution that stirs and carries away whatever is loosened, the more powerful the more turbid the water; this is the most powerful way to move and carry off soil and leave great depth. The eddy b instead gives a wide, not sudden, depth.
A current dying in a dead pool drops its load
Beneath the current the bottom will rise when the current dies within still water. If the river a f pours into the dead pool f n m b, then, since where the course of water fails whatever it carried remains, the material carried by the course a f is left at f b.
Reclaiming a marsh into workable land
A marginal note praises the benefit of silting up and filling a marsh, purging the air, and making workable farmland.