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"Parr II. Szor. ii. §3.] SOLUTION BY RIVERS. 365 
and in a frosty winter; it attains its minimum in rainy seasons and 
after rain. Its amount and composition depend unon the nature of 
the rocks forming the drainage-basin. Where these are on the whole 
impervious the water runs off with comparatively slight abstraction 
of mineral ingredients; but where they are permeable the water, in 
sinking through them and rising again in springs, dissolves their 
substance and carries it into the rivers. The composition of the 
river waters of Western Europe is well shown by numerous analyses. 
The substances held in solution include variable proportions of the 
atmospheric gases, carbonates of lime, magnesia, soda, iron, and 
ammonia; silica; peroxides of iron and manganese; alumina; 
sulphates of lime, magnesia, potash, and soda; chlorides of sodium, 
potassium, calcium, and magnesium; silicate of potash; nitrates; 
phosphoric acid ; and organic matter. The minimum proportion of 
mineral matter among the analyses collected by Bischof was 2°61 in 
100,000 parts of water in the Moll, near Heiligenblut—a mountain 
stream 3800 feet above the sea, flowing from the Pasterzen glacier 
over crystalline schists. On the other hand, as much as 54:5 parts 
in the 100,000 were obtained in the waters of the Beuvronne, a 
tributary of the Loire above Tours. The average of the whole of 
these analyses is about 21 parts of mineral matter in 100,000 of 
water, whereof carbonate of lime usually forms the half, its mean 
quantity being 11°34.2 Bischof calculated that, assuming the mean 
‘quantity of carbonate of lime in the Rhine to be 9°46 in 100,000 of 
water, which is the proportion ascertained at Bonn, enough of this 
substance is carried into the sea by this river for the annual forma- 
tion of three hundred and thirty-two thousand millions of oyster 
shells of the usual size. The minera] next in abundance is sulphate 
of lime, which in some rivers constitutes nearly half of the dissolved 
mineral matter. Less in amount are sodium chloride, magnesium 
carbonate and sulphate, and silica. Of the last named, a percentage 
amounting to 4°88 parts in 100,000 of water has been found in 
the Rhine, near Strasburg. (See p. 453.) The largest amount of 
alumina was 0°71 in the Loire, near Orleans. The proportion of 
mineral matter in the Thames, near London, amounts to about 33 
parts in 100,600 of water.? 
It requires some reflection properly to appreciate the amount of 
solid mineral matter which is every year carried in solution from 
the rocks of the land and diffused by rivers into the sea. Accurate 
measurements of the amount of material so transported are still 
much required. The Thames carries past Kingston 19 grains of 
mineral salts in every gallon, or 1502 tons every twenty-four hours, 
or 548,230 tons every year. Of this quantity about two-thirds 
1 Roth, op. cit. i. p. 454. 
2 Bischof, “Chem. Geol.” i. chap. v. More recently another similar collection of 
analyses, chiefly of European rivers, has been published by Roth, the mean of thirty- 
eight of which gives a proportion of 19°983 in 100,000 parts of water. Op. cit. p. 456. 
8 Bischof, op. et loc. cit.; Roth, op. cit. i. p. 454. For composition of British 
river-water, see “ Rivers Pollution Commission Report.” 
