LOWER CHALK. 137 



here and there, over the Downs. Stone-henge, and other druidical temples 

 are situated upon it, being composed of immense blocks of the siliceous 

 sandstone, that occurs in the form of boulders, on various parts of its 

 surface. 



The description of the South Downs inserted in a former part of this 

 work, will sufficiently explain the range, and extent, of the Upper and 

 Lower Chalk, in the south-eastern part of Sussex ; varying in altitude from 

 300 to upwards of 800 feet, this chain of hills extends from Beachy Head 

 along the coast to Brighton, from whence it stretches through the centre 

 of western Sussex, into Hampshire. On the north it presents a preci- 

 pitous escarpment to the Weald, but its southern side descends with a 

 gentle slope, and on the south-west is lost beneath the beds of the Isle of 

 Wight basin ; while the south-eastern part forms a line of chalk cliflfs of 

 considerable extent. 



The South Downs are intersected by four transverse vallies of con- 

 siderable extent, through which the Arun, the Adur, the Ouse, and the 

 Cuckmere, flow from the interior of the country into the British Channel ; 

 the course of these rivers has abeady been described. 



The general dip or inclination of the strata of the Sussex range, is to 

 the south-east; in a few instances, however, the influence of local causes 

 has occasioned some exceptions. 



The summits of the hills are generally covered with a layer of loose 

 flints, which lies immediately beneath the turf; and in some places, beds of 

 sand and clay, with boulders of sihceous sandstone, and breccia, and other 

 accumulations of diluvial detritus, obtain a similar situation. In numerous 

 places on the sides and at the base of the Downs, quarries have been opened, 

 and kilns erected, for converting the chalk into lime, of which immense quan- 

 tities are annually consumed by the Sussex agriculturists. These partial 

 sections in the interior, together with the line of coast from Brighton to 

 Beachy Head, afford ample opportunities for the examination of the geolo- 

 gical structure of this interesting chain. 



We now proceed to a more particular survey of the deposits included 

 in the present section ; but before entering on their investigation, it may 



