separation of the waters, is good English both in etymology and in spelling.] not less than one hundred and fifty miles--is arrested by the still waters of the Lakes Maggiore and Como, and some smaller lacustrine reservoirs, and never reaches the sea. The Po is not continuously embanked except for the lower half of its course. Above Cremona, therefore, it spreads and deposits sediment over a wide surface, and the water withdrawn from it for irrigation at lower points, as well as its inundations in the occasional ruptures of its banks, carry over the adjacent soil a large amount of slime. [Footnote: The quantity of sediment deposited by the Po on the plains which border it, before the construction of the continuous dikes and in the floods which occasionally burst through them, is vast, and the consequent elevation of those plains is very considerable. I do not know that this latter point has been made a subject of special investigation, but vineyards, with the vines still attached to the elms which supported them, have been found two or three yards below the present surface at various points on the plains of Lombardy.] If to the estimated annual deposits of the Po at its mouth, we add the earth and sand transported to the sea by the Adige, the Brenta, and other less important streams, the prodigious mass of detritus swept into Lago Maggioro by the Tosa, the Maggia, and the Ticino, into the lake of Como by the Maira and the Adda, into the lakes of Garda, Lugano, Iseo, and Idro, by their affluents, [Footnote: The Po receives about four-tenths of its waters from these lakes. See Lombardini, Dei cangiamenti nella condizione del Po, p. 29. All the sediment carried into the lakes by their tributaries is deposited in them, and the water which flows out of them is perfectly limpid. From their proximity to the Alps and the number of torrents which empty into them, they no doubt receive vastly more transported matter than is contributed to the Po by the six-tenths of its waters received from other sources.] and the yet vaster heaps of pebbles, gravel, and earth permanently deposited by the torrents near their points of eruption from mountain gorges, or spread over the wide plains at lower levels, we may safely assume that we have an aggregate of not less than ten times the quantity carried to the Adriatic by the Po, or 550,000,000 cubic yards of solid matter, abstracted every year from the Italian Alps and the Apennines, and removed out of their domain by the force of running water. [Footnote: Mengotti estimated the mass of solid matter annually "united to the waters of the Po" at 822,000,000 cubic metres, 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