436 
SUBTERRANEAN WATERS. 
the aqueous vapors of the air are the ultimate source of supply, 
and all these hidden stores are again returned to the atmo¬ 
sphere by evaporation. 
The proportion of the water of precipitation taken up by 
direct evaporation from the surface of the ground seems to 
have been generally exaggerated, sufficient allowance not 
being made for moisture carried downward, or in a lateral 
direction, by infiltration or by crevices in the superior rocky 
or earthy strata. 
According to Wittwer, Mariotte found that but one 
sixth of the precipitation in the basin of the Seine was 
delivered into the sea by that river, “ so that five sixths 
remained for evaporation and consumption by the organic 
world.” * 
Lieutenant Maury estimates the annual amount of pre¬ 
cipitation in the valley of the Mississippi at 620 cubic miles, 
the discharge of that river into the sea at 107 cubic miles, 
and concludes that “this would leave 513 cubic miles of 
water to be evaporated from this river basin annually.” t 
In these and other like computations, the water carried 
down into the earth by capillary and larger conduits is 
wholly lost sight of, and no thought is bestowed upon the 
supply for springs, for common and artesian wells, and 
for underground rivers, like those in the great caves of 
Kentucky, which may gush up in fresh-water currents at 
the bottom of the Caribbean Sea, or rise to the light of day 
in the far-off peninsula of Florida. 
The progress of the emphatically modern science of geology 
has corrected these erroneous views, because the observations 
on which it depends have demonstrated not only the existence, 
but the movement, of water in nearly all geological forma¬ 
tions, have collected evidence of the presence of large reser¬ 
voirs at greater or less depths beneath surfaces of almost every 
* PhysiJcalische Geographic, p. 286. It does not appear whether this 
inference is Mariotte’s or Wittwer’s. I suppose it is a conclusion of the 
latter. 
f Physical Geography of the Sea. Tenth edition. London, 1861, § 274. 
