1872.] Geology of the Straits of Dover. 221 
What is here suggested is often done on a small scale, 
where a dry mass of rock is known to underlie the surface. 
In quarries the water which collects in the bottom, being 
perhaps held up by an impervious bed of clay, immediately 
beneath the stone that is worked, is often got rid of by boring 
a hole down to a lower porous bed which contains no water. 
Of course this fa¢t must first be ascertained, or the boring 
may bring up more water into the quarry. All well-sinkers 
are, however, familiar with the faét that water found ina 
well at one stratum is often lost if the well be continued 
further down ; and therefore they often rest content with a 
comparatively small supply, rather than continue the well 
further down, and thus risk losing the whole. 
Wet lands, overlying chalk or other limestones, are often 
drained by sinking a pit to such rocks, and conducting the 
surface drains into the pit. Town sewage has been disposed 
of in a similar manner, perhaps to be again pumped up by 
neighbouring deep wells. 
Whether or not the Palzozoic rocks will carry off water 
in the way here suggested can easily be ascertained by ex- 
periment. If they tail to do so, then the water must be 
raised to the surface by pumping. If they do thus carry off 
water, there will not only be an immense saving in the cost 
of pumping, but, what is of far greater importance, there 
will be no danger of a great influx of water drowning out 
the tunnel.* 
One great danger anticipated by some people in driving a 
tunnel beneath the Straits of Dover is, that of meeting with 
some great fault, or enormous dislocation of the strata, to 
which they suppose the formation of the Straits to be due. 
‘There is, however, not the slightest evidence to warrant any 
such anticipation. So far as we can judge from a study of 
the shores the chalk seems to pass evenly across the 
channel-bed, and such examinations of that bed as have 
béen undertaken tend to confirm this opinion. ‘The Straits 
of Dover have been worn through by the slow and long- 
continued action of the waves. It is, however, very likely 
that at one time, when the land stood at a higher level, and 
before the sea had eaten out the Straits, that a river ran 
from south to north through the chalk escarpment, which 
then stretched across from Folkestone to Wissant. The 
higher streams of this old river are the Rother on the 
* I do not wish much importance to be attached to these suggestions; for 
the rocks may be full of water and yet yield no rising water to wells; or they 
may be comparatively dry and yet so compact in structure as to prevent water 
from passing readily through them. 
