HAMPSTEAD HILL— ITS SCULPTURING. 55 



west some marshy ground. This has recently been partly 

 drained, and so deprived, to some extent, of its natural character, 

 to the great regret of many naturalists, but still, especially in the 

 winter, a true river source is well exemplified. The drainage of 

 the uppermost part of this valley is collected in the Leg of 

 Mutton Pond, and afterwards passes on through the miniature 

 valley of erosion before-mentioned to feed the Brent. The old 

 Bayswater and Westbourne stream had its source in the south- 

 west or Oak Hill and Frognal valleys, and the sources of the 

 Fleet on the south-east now supply the Vale of Health Pond 

 and the ponds on the Lower Heath. 



Besides the streams above-named, the sands of the Heath 

 supply by their drainage the water for several well-known springs, 

 which issue on the town side of the hill and mark the uppermost 

 level of the clay. The Conduit Spring near to Rosslyn Bank was 

 long known as a source of good water, but is now injured by the 

 shaft of the railway tunnel. The chalybeate spring near Well 

 Walk has been famous since the beginning of the last century. 

 The chalybeate character of the water is due to the iron oxide of 

 the sands through which the water percolates. It has now but a 

 very small flow, yet the chalybeate impregnation of the water 

 is still very decided. The occurrence of springs or outflows of 

 water round the hill will therefore serve, where no exposure of 

 the beds are to be seen, to determine the approximate position of 

 the junction line between the pervious Bagshot Sands and the 

 underlying London Clay. It follows also that dampness of 

 foundations at a high level, a cause of surprise to many, will be 

 easily accounted for by the geological conditions and structure of 

 the hill. This important line of junction may, however, be 

 actually seen at various points where exposures of the lower strata 

 of the sands occur, notably at North End, at Oak Hill Park, and 

 at the brickyard between Hampstead and Highgate. 



