384 PRINCIPLES OF BOTANY, ETC. 
things came to that state, in which we find them 
now. Most likely our posterity will gaze at simi- 
lar changes in a future period, which nature is now 
slowly preparing. Nature is always changing, al- 
ways operating, and often at a very late period only 
we experience the effects of those changes and 
operations, 
§ 354. 
But before all this took place, was not the sea of 
far greater extent than at present? Perhaps our 
earth then was one sheet of water, interrupted only 
by ranges of lofty mountains, and the depth of the 
sea itself less. Vegetation only existed upon these 
summits. ‘The sea worked gradually deeper in the 
ground, and the mountains became lower, and thus 
gradually the continent was formed, on which now 
the plants of the mountains and those in their val- 
leys became disseminated. Here and there the sea 
left large lakes of sea water, which were gradu- 
ally evaporated, and left the firm fossil-salt be- 
hind. Waves or storm winds covered these beds 
of fossil-salt with earth or with mud, which finally 
became hard and stony. The sea shores nourish 
plants, we know, quite peculiar to them, which only 
agree with saltish ground, and decay in ground 
which contains no salt. Those plants of the sea- 
shore, near beds of fossil-salt, find food enough, and 
propagate themselves.. Subterraneous springs of 
sweet water flowed over those salt beds, dissolved 
part of the salt, and came out from the ground 
as salt water springs. Here likewise the plants of 
the 
