SUBTERRANEAN WATERS. 
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Subterranean Waters. 
I have frequently alluded to a branch of geography, the 
importance of which is but recently adequately recognized— 
the subterranean waters of the earth considered as stationary 
reservoirs, as flowing currents, and as filtrating fluids. The 
earth drinks in moisture by direct absorption from the atmos¬ 
phere, by the deposition of dew, by rain and snow, by percola¬ 
tion from rivers and other superficial bodies of water, and 
sometimes by currents flowing into caves or smaller visible 
apertures.* Some of this humidity is exhaled again by the 
* The caves of Carniola receive considerable rivers from the surface of 
the earth, which cannot, in all cases, he identified with streams flowing out 
of them at other points, and like phenomena are not uncommon in other 
limestone countries. 
The cases are certainly not numerous where marine currents are known 
to pour continuously into cavities beneath the surface of the earth, but 
there is at least one well-authenticated instance of this sort—that of the 
mill streams at Argostoli in the island of Cephalonia. It had been long 
observed that the sea water flowed into several rifts and cavities in the 
limestone rocks of the coast, but the phenomenon has excited little atten¬ 
tion until very recently. In 1833,. three of the entrances were closed, and 
a regular channel, sixteen feet long and three feet wide, with a fall of three 
feet, was cut into the mouth of a larger cavity. The sea water flowed into 
this canal, and could be followed eighteen or twenty feet beyond its inner 
terminus, when it disappeared in holes and clefts in the rock. 
In 1858, the canal had been enlarged to the width of five feet and a 
half, and a depth of a foot. The water pours rapidly through the canal 
into an irregular depression and forms a pool, the surface of which is three 
or four feet below the adjacent soil, and about two and a half or three feet 
below the level of the sea. From this pool it escapes through several 
holes and clefts in the rock, and has not yet been found to emerge else¬ 
where. 
There is a tide at Argostoli of about six inches in still weather, but it is 
considerably higher with a south wind. I do not find it stated whether 
water flows through the canal into the cavity at low tide, but it distinctly 
appears that there is no refluent current, as of course there could not be 
from a basin so much below the sea. Mousson found the delivery through 
the canal to be at the rate of 24.88 cubic feet to the second; at what stage 
of the tide does not appear. Other mills of the same sort have been 
