322 EOCENE PERIOD. [Ch. XXII. 



conclude that the denudation was successive and gradual during 

 the rise of the strata. 



10. We may suppose that the materials carried away from 

 the denuded district were conveyed into the depths of the con- 

 tiguous sea, through channels produced by cross fractures 

 which have since become river-channels, and which now inter- 

 sect the chalk in a direction at right angles to the general axis 

 of elevation of the country. 



11. The analogous structure of the Valley of Kingsclere, 

 and other valleys which run east and west, like the Valley of 

 the Weald, but are much narrower, accord also with the hypo- 

 thesis, that they were all produced by the denuding power of 

 water co-operating with elevatory movements. 



12. The mineral composition of the materials thus supposed to 

 have been removed in immense abundance from the Valley of 

 the Weald, are precisely such as would, by degradation, form 

 the English Eocene strata. 



13. It is probable that there were many oscillations of level 

 during the Eocene period, so that some tracts were alternately 

 land and then sea, and then land again. These fluctuations 

 may account for the furrowed surface of the chalk on which the 

 tertiary strata sometimes repose, for the valleys on its surface, 

 for the banks of shingle associated with the Plastic clay, for 

 the partial deposits of sand and clay on elevated tracts of chalk, 

 and for the alternations of marine and fresh-water strata in the 

 Hampshire basin. 



14. The volcanic eruptions of the Eocene period in Au- 

 vergne, the changes of level which took place at the same time 

 in the Paris basin, and those above alluded to in the south-east 

 of England, may all have belonged to one theatre of subter- 

 ranean convulsion. 



15. The basins of London and Hampshire may have been 

 partly formed by subsidences in the bed of the sea, contempo- 

 raneously with the elevation and emergence of the Weald 

 district. 



