44 BULMAN: DRIFT SANDS AND GRAVELS OF NORTHUMBERLAND. 
carry stones of considerable size; but, reaching the lower ground, 
their burden would be spread out over the boulder-clay. And, as at 
the present day a sudden thaw after a long continuance of frost and 
larger scale, would it be at the close of the Glacial period. The 
waters pent up for centuries, being at last released, would course 
down the valleys with enormous volume and carrying power. In this 
way the great mass of the deposits and the large size of many of 
their contained fragments are accounted f 
The denudation in places of the cadetaie clay, by the same 
forces which accumulated the sand and gravel, would cause the latter 
origin of these sands and gravels be accepted or not, the almost 
total disappearance of morainic matter—which at one time must 
have thickly covered the higher ground——is to be accounted for; 
since scarcely any true moraines are known in the county. And 
there can be little doubt that, granting a Glacial epoch, the vast 
quantities of water released at the melting of the ice wow/d carry 
this morainic débris down to the lower grounds. Arriving at the 
plains of boulder-clay which filled in, altogether or in part, the old 
water-courses, these torrents would lose much of their carrying 
ag! 
became less powerful, and there was less glacial débris for them to 
carry, they would begin to cut out channels in the drift and boulder- 
clay down to the rock beneath, as they are still doing. 
he necessity of supposing that river-action was more powerful 
at the close of the glacial period than it is at present, is thus noted by 
Prestwich :—‘ As the ice melted, the vast volume of water liberated 
by the accumulated ice and snow produced floods, which scored 
the plains and deepened the river-valleys.—Geology, vol. ii, p. 469. 
The fact that the old channels were more or less obliterated 
would cause the sand and gravel to be spread over considerable 
areas, and this peculiarity of the river-action of the period is likewise 
noted by Prestwich :—‘At first these rivers were without definite 
channels, and _ over a considerable breadth of ground.’— 
Tbid, vol. ii. p. 4 
Wright, in nde recently-published Ice Age in North America,’ 
re i e period 
in a short time, tear down and distribute as sediment to distant, 
valleys the materials accumulated by the slow movement of centuries.’ 
Naturalist, 
