270 THE CAUSES WHICH 



sixth century was united to the mainland by the wooded district 

 of Quokeland, now lying submerged with its old Druidical 

 remains. Sunk forests, in like manner, fringe the shores of 

 Sussex, Hampshire, Dorset, Devon, Cornwall, whose trees, iden- 

 tified as oak, elm, chestnut, and hazel, pertain not to a sea- 

 board, and some of these, indeed, appear mid-channel, where, 

 covering the Goodwin Sands, again, is a deposit of clay. 

 Cromer Forest similarly plunges beneath the German Ocean, 

 and after a storm stumps of oak, alder, yew, and Scotch fir, are 

 seeji standing upright in the water. Old terraced beaches lie 

 out at various depths in advance of our shores ; and in the time 

 of Tacitus the Zuyder Zee was a series of freshwater lakes. 

 Farther south, at Sangatte, near Blanc Nez, I have myself noticed 

 an old reed swamp full of the green wing-cases of Doriacia to run 

 under the water. On the contrary, accompanying this general land 

 depression, we have local indications of partial gain of sand-flats 

 and mud land, with the disappearance of ancient river courses, 

 probably due to silting and land drainage, as at Sandwich, 

 Romney, Dungeness, or Calais.* 



It would, then, appear that the first indigenous flora over the 

 northern hemisphere had insular character, with affinity to that 

 existing in Polynesia. During secondary time, according to Pro- 

 fessor O wen, it approached more nearly that of Australia ; and towards 

 the close of this age, according to Professor Dawson, there arose in 

 North America a new and exogenous flora, which, after spread- 

 ing to Europe, became naturalised across the Atlantic. To this 

 flora succeeded on the European area one of Australian and 

 South African type, which on the advent of the Glacial epoch 

 was replaced in Europe by the present Arctic flora, the Arctic 

 flora in turn yielding in process of time to the present vegetation 

 of the ai'ea. We thus learn that Europe in particular has been 

 successively covered with a flora akin to the Polynesian and 

 Australian, with one more or less identical with the AustraHan 

 and South African, the present North American, and the Arctic. 



* For an account of fossil insect hunting in the West of England see the 

 Rev. P. B. Brodie's " History of Fossil Insects." A comprehensive synopsis of 

 the " Insect Fauna in the Geological Periods " has lately been published by IVIr. 

 H. Goss, F.G.S. It must, however, be remarked that zoological species older 

 than the Tertiary cannot be established from the remains, and that the nomen- 

 clature employed by palasontologists merely indicates afSnity in the specimen. 



