694. | GEOLOGY OF OHIO. 
first of the water-bearing horizon named above, but it has been learned 
that this vein is uncertain, and the drilling is now continued until the 
great vein, or that borne by the surface of the Niagara shales, is reached. 
To one or two points of practical importance in this connection atten- 
tion is here called. The veins, or rather sheets, of water found under 
ground are fed from no mysterious sources, but receive their supply, in 
considerable part at least, directly from above. Surface waters traverse 
the shallow, gravelly clay that covers the rocks easily and rapidly, and 
they descend through the porous limestone with almost equal facility. 
But it is often forgotten that all of the water descends, water from drains 
and cess-pools as well as from summer showers or winter snows. In 
point of fact no more effective drain is required for the discharge of ordi- 
nary household water waste than an opening into these gravelly clays 
affords and when the excavation is carried to the surface of the hme- 
stone, the drain discharges its contents with great promptness. The 
ease is bad enough as already stated, but in point of fact it is even much 
worse than it is here represented. If the descending sewage and cess- 
pool water were all obliged to traverse the porous Hmestone before enter- 
ing the veims from which wells and springs are fed, we could be certain 
that it would be quite thoroughly filtered. But the cap rock is not only 
porous, it is also fractured. Like all massive limestones, it is traversed 
by two sets of joints, which divide it into blocks of quite regular shape. 
But partly by solution and partly by contraction and settling, the faces 
of these divisional planes are no longer in contact. Crevices varying 
from an inch to a foot in width intersect the strata. They are generally 
filled with gravelly clay, but they allow. a very free transmission of 
liquids from above. A very gross and dangerous communication is thus 
established between the neglected or polluted surface and the water veins 
depended on for daily use. | 
It has been abundantly demonstrated that drinking water contam- 
inated with even a very minute proportion of undecomposed exeretory 
matter becomes a common carrier of disease. Cholera and typhoid fever 
in particular are known to be very largely distributed in this manner. 
The addition of one grain of sewage defilement to the gallon was found, 
in the cholera epidemic of 1866, in London, to be directly connected 
with 71 per cent. of the whole mortality. The fact that cholera has 
wrought its worst ravages in this country in places quite similar in 
geological structure to the areas now under discussion is well known. 
The names of Sandusky, of Nashville, of Murfreesboro, of Paris, Kentucky, 
of Covington, Indiana, will recur to the minds of all. There 1s weighty 
reason for believing that the fatality of the disease in all these widely 
