136 LOWER CHALK. 



" The third range, leaving Wiltshire and Berkshire, enters Hants, and 

 to the south passes round Petersfield, then, stretching to the east, forms 

 a barrier against the sea along the coast from Chichester and the South 

 Downs as far as Dover, and ranges from Maple-Durham, Houghton, 

 Steyning, and Lewes, as far as Beachy Head*." 



Insular parts occur in the Isle of Thanet, and Isle of Wight -f-. 



In France the chalk prevails on the skirt of the western boundary of 

 Mount Jura, extending nearly in a direction from S. E. to N.W., and 

 covering a space of at least 210 miles long, and 50 broad. 



Chalk also occurs in Ireland, Saxony, Spain, Denmark, Sweden, and 

 Poland:}:. 



The thickness of the chalk formation varies considerably in different 

 parts of its course. Near Royston it attains an elevation above the sea 

 of 481 feet; south of Dunstable, it is 994 feet; south of Shaftsbury, 941 

 feet ; between Lewes, in Sussex, and Alton, in Hampshire, various parts 

 of the range rise to the height of between 800 and 900 feet ; and be- 

 tween Alton and Dover, between 700 and 800 feet §. In the Sussex range 

 Ditchhng Beacon, which is the highest point, is 856 feet above the level 

 of the sea. 



The mountain ranges formed by the chalk, are characterized by their 

 smooth and unbroken outline, and are generally covered with a short 

 verdant turf ||. 



The earher inhabitants of this island, either from choice or necessity, 

 fixed their settlements on the elevated ridges and platforms of this form- 

 ation ; and vestiges of their sepulchral mounts are still visible scattered 



* Townsend's Moses, Vol. i. page 142. 



•f Smith's Strata. For a more particular account of the range and extent of the chalk 

 formation, vide Phillips Geological Outlines, edition 1822, page 77. 



J Dr. Berger, Geological Transactions, Vol. i. page 14. 



§ Phillips' Uutlines, 2d edition, 1816. 



II " In Champagne, in France, there are immense plains of chalk absolutely destitute of 

 vegetation, except where patches of the Calcaire grassier occur as islands, or oases in the midst 

 of these deserts. Many parts of this tract have perhaps not been visited for ages by any living 

 being, no motive existing that could induce any one to wander there. This chalk is said to 

 contain 11 per cent, of magnesia, to which the barrenness of the soil is supposed to be owing." 

 Geological Transactions, Vol. ii. p. 175. 



