MOETBIER : OEIGIN OF CHALK DALES. 
31 
along lines of bedding in continuous sheets, and in some places in 
little streams along- open joints. This is a feature observable all 
along the chalk cliff wherever its base is swept clean of debris. 
These streamlets have escaped from the rock, between the existing 
tide-lines, ever since the sea and land held their present positions, 
yet there is no well marked symptom that any subterranean channel 
is being excavated by this natural underground drainage. 
Along the out-cropping edge of the chalk, springs of water 
would then as now escape from the edge of hollows on the surface 
of the clays immediately under the chalk, or where the foot of the 
out-cropping chalk was the least covered with obstructing debris. 
These springs have been running ever since the chalk hills were 
pushed into their present position, without having denuded the chalk 
more than a few feet, or formed any visible subterranean channel, 
except in rare cases ; moreover, the springs which are now found in 
valley bottoms, do not, in any case, to my knowledge, escape from 
the head of the valley, but from the upthrown side of the 
valley, and sometimes near where the side juts a little into the 
valley bottom, as at Thixendale and Burdale, where there is no trace 
of eating back in the form of an incipient side-dale. Besides these 
streams only run in the valley bottoms where the Kimmeridge or 
Neocomian clay happens to reach the surface, and as soon as that falls 
below the surface, the streams disappear and sink to the water- line 
in the chalk. The same holds good for the gypsey valley, the 
stream is only observed on the surface when clay is immediately 
underneath, except after much rain, when the subterranean water- 
line frequently' rises and floods the surface, and then runs along a 
hollow or drains on the surface until it meets with higher ground, 
where it disappears for some distance, and becomes part of the 
subterranean water-sheet, after which it again appears on the surface. 
There is no visible appearance that such higher chalk ground is being 
excavated. This is just what would occur in former times ; and I 
repeat that in such a small area as the Wolds, streams could not 
exist of sufficient power to excavate the existing valleys. Besides, 
to do this, such imaginary streams would have had to run in opposite, 
and in every direction. 
