INTRODUCTION. 3 



^ii the numerous ancient valleys and river-channels which are 

 met with in various parts of the country, running at depths of 

 from one hundred to more than two hundred feet below the 

 present level, and frequently cutting right across the present 

 lines of drainage, and connecting valleys now completely 

 separate. Completely choked with deposits of sand and mud, 

 and showing no evidence of their existence in the present con- 

 figuration of the country, these ancient drainage channels have 

 been revealed to us by the borer, and afford incontestable 

 evidence of a very extensive subsidence. The evidence of this 

 submergence indicates, therefore, that at no very distant epoch 

 portions, at least, of the land must have stood at least two 

 hundred and fifty feet higher above the sea than they do at 

 present, and probably considerably more ; and such an eleva- 

 tion would, in the opinion of Dr. Wallace, have been amply 

 sufficient to unite England with the Continent. 



We may admit, then, that during, or about, the period when 

 the Norfolk forest-bed (which, we may state, antedates the 

 Glacial epoch) was deposited, the British Islands were connected 

 with the Continent, and doubtless also with one another. And 

 it would appear from the researches of palaeontologists that 

 their Mammalian fauna was then in all probability identical, 

 or nearly so, with that of the Continent. For, instance, apart 

 from a host of extinct species, into the consideration of which 

 it will be unnecessary to enter on this occasion, it appears that 

 during the forest-bed period there existed in England the 

 Russian Desman {MyogcUe inoschaia\ the Continental Field- 

 Vole (Microlus arvalis)^ and the more arctic Glutton {Gido 

 lusais) and Musk-Ox {Ovibos mo., hat us). And there is evidence 

 that at the later period of the caverns and brick-earths there 

 were many olher Continental forms, such as the Lemming 

 ( Omiculus iorqiiatus)^ two species of Suslik {Spermophilus)^ the 

 Elk {^Alces machlis)^ the Reindeer {Raftgifer tarandus)^ &c., &c. 



B a 



