58 THE WORLD'S LUMBER ROOM. 



mountains and rushing down in numberless torrents to the 

 valleys. It is when the snows melt that the Rhine is at its 

 fullest and muddiest, and often causes the waters of Lake 

 Constance to rise as much as a foot in twenty-four hours, 

 and the mineral which it chiefly conveys is carbonate of 

 lime, which constitutes more than a third of the deposit left 

 in the lake. On leaving the lake, the Rhine again passes 

 through miles of limestone, as do also its tributaries, and 

 yet the sediment which it finally takes to the ocean con- 

 tains little or none. It does carry it, indeed that we may 

 be sure of and in considerable quantities, too, but not as 

 visible sediment, for it has been dissolved by the carbonic 

 acid of the water and thus rendered invisible 



Up to the time when it reaches the lake, the course of 

 the river is so rapid and tumultuous that the carbonic acid 

 has but little chance of doing anything, and the powdered 

 limestone is simply carried down as sediment thus far. On 

 leaving the lake, however, the river has a long course before 

 it, and when it reaches the sea all the carbonate of lime 

 which itself and its various tributaries have collected, and 

 even all that is washed into it in time of flood, has been so 

 completely dissolved that we should not be aware of its 

 presence but for the hardness it has given to the water. 



Next to carbonate of lime, the mineral which is carried 

 down to the sea in the largest quantity is sulphate of lime, 

 which never fails entirely except in the case of a few small 

 rivers. But we shall gain a better idea of the amount of 

 mineral matter removed by the rivers when we come to see 

 what is done with it ; meanwhile we may mention, for those 

 who like statistics, that such rivers as the Danube, Rhine, 



