116 



ROYAL HORTICULTURAL SOCIETY. 



all its sources are derived from dark peat-moors, from which the water 

 streams coloured brown from their dissolved humous constituents. 

 The same is the case with the other rivers of the Upper Hart/,, 

 especially on the north side of the Brocken. Almost all the fresh- 

 water lakes of the marsh districts of Northern Germany are black 

 from humous matter. 



I have endeavoured by means of evaporation to ascertain the 

 quantity of humus in different German river-waters. Pour 

 pounds and a half of that of the Spree yielded, on evaporation, 

 4 grs. of solid residuum, of which three consisted of salts, the other 

 of a humous extract. The Spree water is, for the most part, not 

 entirely colourless, but has a yellowish tint; on evaporation it 

 acquires a brown tint as it becomes more concentrated. Every 

 pound of it contains f gr. of humous extract ; a cubic foot, there- 

 fore, or 66 lbs., contains 14-f grs. According to observations made 

 at the Berlin Mills, 576 cubic feet pass every second at low flood, 

 2016 at high flood, the mean of which is 1296. 



At low flood, then, there are 2,072,600 cubic feet per hour, or 

 49,766,400 cubic feet per day, or in weight 29,859,840 cwt. This, 

 then, contains 49,766,400 x 141^729,907,200 grs. or 422 cwt. 

 100 lbs. of humous extract, which quantity passes through Berlin 

 on its way to the sea. 



The turbid water of the Elbe, collected at Magdeburg in August 

 1851, became clear when allowed to settle, with a very slight 

 yellow tint. Eour pounds of this evaporated to a coffee-brown 

 fluid ; and this, when freed from the sediment of salts of lime and 

 silicates, yielded 6| grs. of humous extract, free from water. The 

 Elbe water is therefore far richer in humus than that of the 

 Spree — the richest, indeed, of all which I have examined, although 

 it is by no means so deeply coloured as the Hartz water. It con- 

 tains more than 1 1 gr. of humous extract per pound, which in the 

 cubic foot amounts to 107^ grs. If w^e assume that 4000 cubic 

 feet per second pass by Magdeburg to the sea, which is double 

 that of the high flood of the Spree, we have for the twenty-four 

 hours 14,400,000 cubic feet, and this will supply daily, if 100 grs. 

 of humus only be reckoned to the cubic foot, about 1798 cwt. 

 of extractive matter which can be appropriated to the nourish- 

 ment of plants. "We see then how rich the waters are in 

 nutriment. 



The water of the Use, at Ilsenburg, collected in August 1851, 

 gave, after the evaporation of 4 lbs., 2 grs. of humous extract, 

 which is | gr. per pound. 



