50 HAMrSTEAD HILL. 



and Harrow, vvc find the relative level of the previously con- 

 tinuous and far-extending sheet of super-imposed and over- 

 lying Bagshot Sands. 



Hampstead is not, however, a portion of the northern 

 boundary of the Thames Valley, but a hill which, with the 

 adjoining one of Highgate, forms a hill-mass standing within 

 the great Thames Valley some distance to the south of the 

 bounding ridge, and, having evidently been the result of denu- 

 dation on all sides, forms a good example of a hilly mass left 

 standing above the surrounding country by circumdenudation. 



The Bagshot Sands generally constitute the middle division 

 of the English Eocene Tertiaries, which is represented by most 

 important massive and wide-spreading rocks on the continent 

 of Europe and in Asia and Africa, for to the Middle Eocenes 

 belong the well-known Paris building-stone, the Calcau^e gras- 

 sier, extensive beds in India and the Nummutitic Limestone of 

 Egypt used by the builders of the Pyramids. And as rocks of 

 later age form portions of the Alps as high as 5,000 and 

 6,000 feet above the level of the sea, as well as large portions 

 of the Himalayas, the highly-interesting and important fact is 

 ascertained that the sands of Hampstead Heath and, indeed, 

 all the materials of Hampstead Hill were deposited before the 

 most prominent features of the present surface of the Old World 

 came into existence. 



On the surface of the highest part of the Heath, near the 

 Spaniards, will be found some rounded pebbles, thought to be 

 remnants of gravels similar to those which lie on the hill-tops 

 on the north of Middlesex, and named by Mr. Whitaker " Pebble 

 Gravel." They are doubtfully attributed to glacial action, and 

 deemed to be the oldest of the Glacial Deposits. One or two 

 patches on the northern side of the hill have been referred to 

 the Glacial Period, but, with these possible exceptions, the Glacial 



