162 NEOZOIC TIME. [CHAP. IX. 



conclude, therefore, that it was a large lake or mere which 

 occupied an area of newly-emerged and low-lying ground, 

 and that its level was maintained by the local rainfall, not 

 by the influx of a large river. 



My attention has been directed to an essay by Professor 

 Hebert, 1 in which he discusses the physical history of the 

 Jurassic period in France. He divides it into two portions 

 a period of depression and a period of upheaval. He 

 considers that the former only lasted till the time of the 

 Great Oolite, and that the Jurassic sea then attained its 

 greatest superficial extension. Instead of admitting a fur- 

 ther submergence at the time of the Oxford Clay, he attri- 

 butes its absence over the exposed Great Oolite area to 

 non-deposition, and thinks the Oxfordian sea was limited 

 to the Parisian gulf, the sea-space becoming smaller and 

 smaller during succeeding epochs, till it was finally upraised 

 in Purbeck times. 



To most English geologists this must seem a very crude 

 and antiquated view, but I am surprised to find that Pro- 

 fessor Gosselet and other French geologists hold similar 

 opinions, and interpret the geologial record of other systems 

 on the same principles. (See Gosselet's " Esquisse Geol. 

 du Nord de la France.") 



1 " Les Mers Anciennes et leur Kivages dans le Bassin de Paris. 

 Part I. Terrain Jurassique." 1857. 



