Ch. XXIII.] FORMER CONTINENTS WHERE NOW SEA. 329 



respecting the different circumstances under which we conceive 

 the secondary and tertiary strata to have originated. We have 

 there hinted, that the former may have been accumulated in an 

 ocean like the Pacific, where coralline and shelly limestone are 

 forming, or in a basin like the bed of the western Atlantic,, 

 which may have received for ages the turbid waters of great 

 rivers, such as the Amazon, and Orinoco, each draining a con- 

 siderable extent of continent. The tertiary deposits, on the 

 other hand, may have been accumulated during the growth 

 of a continent, by the successive emergence of new lands, and 

 the uniting together of islands. During such changes, inland 

 seas and lakes would be caused, and afterwards filled up with 

 sediment, and then raised above the level of the waters. 



That the greater part of the space now occupied by the 

 European continent was sea when some of the secondary rocks 

 were produced, must be inferred from the wide areas over 

 which several of the marine groups are diffused ; but we do 

 not suppose that the quantity of land was less in those remote 

 ages, but merely that its position was very different. In the 

 above tabular view of the secondary rocks, we have shown 

 that immediately below the division No. 1, or ' the chalk and 

 green-sand,' is placed a fresh-water formation called, in the 

 south-east of England, the Wealden. This group has been 

 ascertained to extend from west to east (from Lulvvorth Cove 

 to the boundary of the Lower Boulonnois) about 200 English 

 miles, and from north-west to south-east (from Whitchurch to 

 Beauvais), about 220 miles, the depth or total thickness of the 

 beds, where greatest, being about 2000 feet *. 



Now these phenomena most clearly indicate, that there was 

 a constant supply in this region, for a long period, of a consider- 

 able body of fresh water, such as might be supposed to have 

 drained a continent, or a large island, containing within it a lofty 

 chain of mountains. Dr. Fitton, in speaking of these appear- 

 ances, recalls to our recollection that the delta of the newly-dis- 

 covered Quorra, or Niger, in Africa, stretches into the interior 



* Fitton's Geology of Hastings, p. 58, 



