372 THE WONDERS OF GEOLOGY. Lect. IV. 



The quarries around Tilgate Forest, where the calcife- 

 rous grit is worked, present the following section : — 



1. Ujypermost Loam or clay — from one, to five or six feet in depth ; 



destitute of fossils. 



2. Sandstone of various shades of fawn, yellow, and ferruginous 



colour; in laminae, or thin layers, occasionally containing 

 organic remains and pebbles ; eight feet thick. 



3. Calciferous grit, or Tilgate stone — a very fine sandstone, formed 



of sand cemented together by calcareous spar ; it occurs in 

 large masses of a concretional form, imbedded in soft sandstone. 

 This grit has evidently been formed by the percolation of water 

 charged with calcareous matter into loose sand ; it abounds in 

 bones and teeth of reptiles ; stems and leaves of plants ; 

 shells, &c. 



4. Sandstone, with concretionary masses of grit ; and conglomerate 



formed of rolled pebbles of sandstone, jasper, quartz, rock- 

 crystal, indurated clay, bones and teeth of reptiles, and of 

 fishes ; rolled masses of the grit and sandstone are found in 

 this conglomerate ; the organic remains which it contains are 

 generally much waterworn. 



5. Blue clay and marl — depth unknown. 



This is the usual series of strata exposed in the quarries 

 around Cuckfleld, Lindfield, Bolney, &c. Near Horsham 

 the fawn-coloured sandstone is more compact, and of a 

 slaty structure. The thin slabs are used for roofing, and 

 the thicker ones for pavements ; their surfaces are some- 

 times deeply furrowed or rippled ; an appearance upon 

 which I will here offer a few observations. 



8. Ripple-marks on sandstone. — The furrowed surface 

 of the sandstones and grits which are used for paving in 

 Horsham, Crawley, and other towns and villages on the 

 Forest-ridge, must have attracted the attention of most 

 persons who have travelled from Brighton to London. The 

 appearance of these slabs, is similar to that presented by the 

 sand along the sea-shore at low water, when the ripples 

 occasioned by the receding waves have been deeply im- 

 pressed ; the markings on the stone have arisen from a 

 similar cause. In many instances the surface is so rough, 



