But what has this to do with sculpture or cutting out of valleys?
If you will only take a glass of water out of any river, and let
it stand for some hours, you will soon answer this question for
yourself. For you will find that even from river water which
looks quite clear, a thin layer of mud will fall to the bottom
of the glass, and if you take the water when the river is
swollen and muddy you will get quite a thick deposit. This shows
that the brooks, the streams, and the rivers wash away the land
as they flow over it and carry it from the mountains down to the
valleys, and from the valleys away out into the sea.

But besides earthly matter, which we can see, there is much
matter dissolved in the water of rivers (as we mentioned in the
last lecture), and this we cannot see.

If you use water which comes out of a chalk country you will find
that after a time the kettle in which you have been in the habit
of boiling this water has a hard crust on its bottom and sides,
and this crust is made of chalk or carbonate of lime,
which the water took out of the rocks when it was passing
through them. Professor Bischoff has calculated that the river
Rhine carries past Bonn every year enough carbonate of lime
dissolved in its water to make 332,000 million oyster-shells,
and that if all these shells were built into a cube it would
measure 560 feet.



Week 14