DE kance: u.nl>ekguuund water-supply and kiver floods. 213 
one which, though impervious, overlies pervious rocks, that can be 
drawn from by artesian wells, or discharged into by dumb wells, into 
which the land-drains might discharge, and replete the strata 
beneatli with water that would otherwise have passed off as devasta- 
ting floods, and thus increase the summer discharge of the streams, 
and turn the intermittent springs into springs of permanent value. 
Should dumb-wells become common it will be necessary to use 
great care that communication is not set up between drains carrying 
objectionable matter and the underground slieet of water, and that in 
drawing water from wells and bore-holes that the point at which 
the water is abstracted is sufficiently removed from the surface to 
insure the water being naturally filtered by passing through the 
superincumbent strata. 
The alternating character of the Millstone (jrit, of permeable 
and impermeable material, and the deep ravines with which it is 
generally intersected render it pecidiarly suitable to the sinking of 
dumb-wells in the shale areas, to conduct the rainfall of the imper- 
meable portion down into the porous rocks beneath when it can be 
stored. They are also valuable for giving a pure and permanent 
supply of water to wells and borings, there is strong reason to believe 
that Underground Water from this source will be more and more 
utilized, and this wouhl be still more likely to be the case if the 
natural percolation into the porous outcrop were aided by dumb-wells 
through the impermeable cover. Reservoirs having to be constructed 
of large size, to enable them to last out droughts, necesssarily occupy 
a considerable area of the best land in a hilly district, often of a 
character well suited to provide food stuff for cattle, a matter of 
great importance in a country containing so small an area as England, 
and consequently obliged to import a large portion of its food supplies. 
The Coal Measure Sandstones of Yorkshire often yield good 
supplies of fresh water, when not contaminated with water from coal 
workings ; the water so derived is bounded by faults, which divide the 
country into water-tight compartments. The fissure of the faults, 
traversing strata of an impermeable nature, becomes filled with it 
and constitute a water-tight barrier. 
The Triassic and Permian formations of England and Wales 
are capable of yielding not less than a daily average of 3,000 million 
