§ 2. FORMATIONS OF THE SECONDARY EPOCH. 295 



existing islands and continents are principally composed ; 

 the fathomless depths of the ancient seas are spread before 

 us, and the relics of innumerable myriads of beings which 

 lived and died in their waters, and became entombed in their 

 profound abysses, remain, like the mummies of ancient 

 Egypt, the silent yet eloquent teachers of their own event- 

 ful history. 



A reference to the Tabular Synopsis (p. 200), will show 

 that the secondary formations constitute ten principal 

 subdivisions ; viz. the Cretaceous, Wealden, Oolitic and 

 Liassic, Tr lassie, Permian, Carboniferous, Devonian, 

 Silurian, and Cumbrian systems, each containing littoral, 

 and oceanic deposits ; sandstones having been formed amidst 

 the agitated waters of the sea shores ; clays in tranquil 

 bays and gulfs ; and limestones in deep water. I purpose, 

 in the present discourse, to explain the geological characters 

 of the first two of the series, namely, the Chalk and the 

 Wealden.* The former is composed of rocks that have 

 been accumulated in the depths of a sea of great extent ; 

 the latter, of the sediments of a vast delta ; the one afford- 

 ing a striking illustration of the nature of oceanic, and the 

 other of jiuviatile deposits. As both the Chalk and the 

 Wealden are fully developed in the south-east of England, 

 the phenomena about to be described may be readily 

 examined, and collections of the peculiar fossils of these 

 formations obtained, with but little trouble. t 



* The term Wealden is derived from the German Wald, signifying 

 a Wood or Forest The Weald of Sussex was formerly an impenetra- 

 ble forest, called Anderida by the Romans, and Andreadsicald by the 



f Since the earlier editions of this work, the Author's extensive col- 

 lection of the Fossils of the south-east of England has been purchased 

 by the Trustees of the British Museum. A brief compendium of 

 its contents was published by the Sussex Royal Institution, under 

 the title of "Descriptive Catalogue of the Mantdlian Museum at 

 Br'ujldoa" 8vo. Brighton, 1836 : fifth edition. 



