248 GENERALIZATIONS. 



stratum the land had sunk down beneath the sea, even though 

 a uniform and regular appearance may be presented by the 

 rocks. 



The alternation of freshwater and marine deposits, like un- 

 conformity of stratification, shows us that changes of level took 

 place at various times, and must have exerted the greatest in- 

 fluence upon the configuration of the land. 



The anthracite-schists with their land plants are covered in 

 many cases (as near Petitcceur) by marine Liassic strata, and 

 must therefore have been under the sea during the Lias period. 

 Hence in the Liassic district a depression took place after the 

 Carboniferous period. From the period of the Trias, however, a 

 rising of the land is to be recognized in Northern Switzerland, 

 since the Keuper follows upon the marine Mussel- Limestone 

 (vol. i. p. 47) . This rising continued up to the middle Scham- 

 belen beds of the Lower Lias, which represent the maximum of 

 elevation (vol. i. p. 67) ; and then commenced a sinking of the 

 land, which must have taken place pretty rapidly, seeing that 

 the land formation of Schambelen is overlain by marine strata, 

 which contain the same species of animals as the lower marine 

 deposits. 



This sinking of the land continued till the time of the 

 Brown Jura. During the deposition of the White Jura a 

 gradual upheaval again took place, and this attained its maxi- 

 mum at the close of the Jurassic period. The whole chain of 

 the Swiss Jura rose from east to west out of the sea, and 

 became dry land. We have, however, already shown (vol. i. 

 pp. 171, 172) that during this long period many oscillations 

 occurred, so that within its limits secondary upheavals and 

 depressions may be recognized. The final result was an up- 

 heaval, the effects of which are displayed in France, Germany, 

 and England, and must therefore be described as a continental 

 movement. It attained its maximum at the time of the forma- 

 tion of the Wealden. Then a depression of the ground again 

 occurred ; as early as the Valangian stage the sea penetrated 

 once more into the south-west of Switzerland, and, gradually 

 spreading further and further, no doubt in consequence of a 

 continued sinking of the ground, attained its maximum in the 



