PRE-GLACIAL PERIOD. 183 



and the fossils which belong to this period in the basins of Lon- 

 don and Hampshire is complete, and we lose an important link 

 in the chain of life-periods. The fact is positive, the explana- 

 tion not so. Perhaps while the Palseotherium and Anoplothe- 

 rium were roaming by the freshwater lakes of the south, and the 

 innumerable shells, so like those of the existing ocean, so unlike 

 all of earlier date, were in the sea which occupied what is now 

 the valley of the Thames, our Yorkshire hills may have stood 

 above the waves. 



This appears the more probable if we remember that the next 

 series of deposits known in the south of England, the Coralline 

 Crag, is also unknown in Yorkshire, and that only the later, 

 perhaps the very latest of the Crag deposits, corresponding to 

 the Mammaliferous Crag of the Eastern counties, has been found 

 in our coast sections at Bridlington. According to this suppo- 

 sition, after the deposition of the chalk, the land was raised 

 again gradually there is at least no trace of violent movement 

 and remained very long above water, divided into islands by the 

 long sea-channel of the Vale of York, and the shorter gulf of 

 the Vale of Pickering. 



In this condition of things the land of Yorkshire is in the state of one 

 great mass on the west, and two smaller masses on the east, one of which, 

 the Wold (W), is shown. The sea flows down the vale of York (Y), and 

 covers Holderness, H. L 1 is the sea-level. 



In the glacial period which follows, the land is depressed again, so that L 2 

 may be the sea-level as measured on the land. 



PRE-GLACIAL PERIOD. We have thus the main elements of 

 the land of Yorkshire defined, and rendered suitable for the re- 

 ception of animal and vegetable life. Plants and animals 

 appeared upon it, not, we suppose, by creation here, but by trans- 

 ference of seeds through air and water, and by the various modes 



