Note 230 — Chapter III · (continued 3)
Reading edition
Mengotti estimated the mass of solid matter annually "united to the waters of the Po" at 822,000,000 cubic mètres, or nearly twenty times as much as, according to Lombardini, that river delivers into the Adriatic. Castellani supposes the computation of Mengotti to fall much below the truth, and there can be no doubt that a vastly larger quantity of earth and gravel is washed down from the Alps and the Apennines than is carried to the sea.—Castellani, Dell' Immediata Influenza delle Selve sul corso delle Acque, i, pp. 42, 43.
I have contented myself with assuming less than one fifth of Mengotti's estimate.