§14. CHARACTERS OF THE TERTIARY. 219 



stances under which deposits were accumulated.* I return 

 from this digression to the consideration of the phenomena 

 presented by the several groups of the tertiary formations. 



14. LlTHOLOGTCAL CHARACTERS OF THE TERTIARY 



strata. — The predominating characters of the tertiary 

 system are alternations of marine beds with those of lacus- 

 trine and freshwater origin. A large portion of the beds 

 is arenaceous, with intervening strata of clay and marl. 

 Shingles, the remains of ancient sea- beaches, abound in 

 some localities, and often occur as a conglomerate or 

 puddingstone, as in Hertfordshire (p. 101) ; or as a ferru- 

 ginous breccia, as at Castle Hill, near Newhaven, on the 

 Sussex coast. f The ruins of the Chalk are everywhere 

 recognizable in the immense beds of water-worn flints, 

 which contain shells and zoophytes peculiar to the cretaceous 

 system. Large erratic boulders and blocks of crystalline 

 sandstone are of frequent occurrence on the chalk downs, 

 and have probably been derived from the upper beds of the 

 Bagshot sand. In the vicinity of Brighton, blocks of ferru- 

 ginous breccia are scattered over the surface of the Downs, 

 and masses of quartzose sandstone, of a saccharine structure, 

 occur at Falmer, and in Stanmer Park : some years since 

 there was a large rock of this stone in Goldstone Bottom, 

 near Brighton. 



In most of the gravel beds around London there are 

 numerous blocks of siliceous breccia and conglomerate. In 

 some of the tertiary series limestone predominates, and 

 alternates with sands and marls of great variety and 

 brilliancy of colour ; beds of gypsum, and siliceous nodules 

 resembling the flints of the chalk, also occur. Such are 



no conclusive evidence that the so-called azoic strata were formed 

 before the existence of animated beings, or that any beds of later 

 data, destitute of fossils, were deposited in deeper water than many of 

 the fossiliferous deposits. 



* See Medals of Creation, vol. i. p. 363. 



f Geology of the S. E. of England, p. 55. 



