By the Rev. W. R. Andrews, F.G.S. 265 
Over this plain the original stream found its way, taking probably 
a more serpentine course than it does now. Cutting its channel in 
the less-consolidated part of the Upper Green Sand, and easily 
washing away its loose material, there soon would be left standing 
a small bank on either side, and gradually there would be formed 
steep escarpments which bounded the main stream on either 
side. 
In the course of time the erosive action of the river cut its way 
entirely through the Upper Green Sand and deep into the soft Gault 
Clay beneath, and then it was able to produce a much greater effect 
than before, for as it washed away the clay at the base of the sand, 
masses of the sand above must have slipped down the sloping side 
of the escarpment. 
In this way the river has cut back the Upper Green Sand, it has 
undermined its support, and much material has in consequence 
slipped down upon the top of the Gault, part of which was carried 
away by the force of the stream, while some now remains strewn 
over the surface of the Gault, and obscuring that formation. 
The cutting back of the Green Sand has progressed until the 
extremely hard beds of Chert, near the top, were reached, which 
now form the top edge of the escarpment. This we may see if we 
view the vale from some high position on the Chalk hills, looking 
westwards, for we shall observe on either side these Green Sand 
hills terminating somewhat abruptly. Thus we get these steep-sided 
hills, too steep for cultivation, and which now, covered with wood, 
add so much to the beauty of the vale. 
The Chalk escarpments of the vale were started by the erosion 
of the Nadder as banks, when it serpentined over the intervening 
Green Sand; but, when the main stream no longer touched their 
base, as it was kept within the channel it had cut in the Gault, 
longitudinal streams flowing into the side streams continued the 
erosion. The water-level at that time stood higher in the Chalk 
hills than it does now, and issuing as springs flowed right and left, 
still further cutting away the base of the Chalk. Before the Broad 
Chalke valley was cut down so deeply springs would be thrown out 
along the south Chalk downs, as they are now on the northern side, 
