FUNCTIONS OF THE ATMOSPHERE. 557 
Nearly three fourths of the Earth being* co- 
vered with Sea, whilst the remaining dry land 
is in need of continual supplies of water, for the 
sustenance of the animal and vegetable king- 
doms, the processes by which these supplies are 
rendered available for such important purposes, 
form no inconsiderable part of the beautiful and 
connected mechanisms of the terraqueous Globe. 
The great Instrument of communication be- 
tween the surface of the Sea, and that of the 
Land, is the Atmosphere, by means of which a 
perpetual supply of fresh water is derived from 
an Ocean of salt water, through the simple pro- 
cess of evaporation . 
By this process, water is incessantly ascending 
in the state of Vapour, and again descending in 
the form of Dew and Rain. 
Of the water thus supplied to the surface of 
the land, a small portion only returns to the Sea 
directly in seasons of flood through the channels 
of Rivers ;* 
A second portion is re-absorbed into the Atmos- 
phere by Evaporation ; 
A third portion enters into the composition of 
Animal and Vegetable bodies ; 
* It is stated by M. Arago, that one third only of the water 
which falls in rain, within the basin of the Seine, flows by that 
river into the sea : the remaining two thirds either return into 
the atmosphere by evaporation, or go to the support of vegetable 
and animal life, or find their way into the sea by subterraneous 
passages. Annuaire, pour I'An 1835. 
