CHAPTER VIII. 



IIAMPSTl^AD 1111. L — ITS SCULrXURING. 



Subsequent to the Glacial Period, the extensive denudation 

 occurred that completed the excavation of the great Thames 

 Valley, as well as that of the subsidiary and lateral valleys of 

 the Brent, the Yedding, and the Colne, in the middle and west 

 of Middlesex, and of the Lea on the eastern side of the county. 

 The land in this district was thus left sculptured as we now see it, 

 with Hampstead, Highgate, and Harrow Hills standing in the 

 midst, and preserving remnants of the great sheet of Bagshot 

 Sands. 



The sculpturing produced by water action is beautifully seen 

 around the Heath. From the summit, valleys radiate to the 

 north-west, to the south-west, to the south-east, and to the east. 

 Each of these valleys gives rise to springs in its upper part 

 by the outflow of water from the base of the sands, consequent 

 upon the stoppage of vertical percolation by the impervious clay 

 beds below. From these outflows of the water of the summit- 

 sands are produced sources of a feeder of the Brent, of the 

 Bayswater and Westbourne, and of the Fleet River. Of these 

 streams the afiluent of the Brent is the only one now flowing 

 along its original natural channel, which may be seen below 

 the Leg of Mutton Pond, forming a very beautiful example 

 of a "valley of erosion." 



Just below the junction of the Bagshot Sands and the London 

 Clay, and on the area occupied by the Upper Sandy Clay, will be 

 found in the valley on the West Heath commencing below the 

 flag-staff, near Jack Straw's Castle, and opening out to the north- 



