German Ocean lately Dry Land. 465 



between Dover and Calais, much as the drawing of the rivulet in Ecclesboum Glen 

 gives an idea of Niagara Falls. From close examination of small valleys we may 

 learn a great deal about larger valleys. The abstraction of water to make ice for 

 collection on the land in the glacial period must have dried the channels and 

 coasts of England to what is now the hundred fathom line. I have many years 

 since surveyed from Shakspeare's Cliff, the Channel — which I believe was once 

 a watershed, bored and pierced by many rivers and brooks in a cold and after- 

 wards very wet period : I can speak particularly of the effect of the landscape 

 from Dover and from Cape Blancnez upon my own mind, and of the stillness of 

 those treeless chalk downs— not plains of chalk, but a series of headlands and 

 large coombes rising to 600 or 700 feet above the sea. In this watershed, 

 now drowned, were once the -sources of two large rivers or glaciers ; one 

 passing round the east coast of England and receiving the Thames, Somme,* 

 Rhine, Maes, Scheldt, Humber, Forth, &c. as tributaries, and passing to the 

 Hebrides ; the other river or glacier at one time passing along the south coast 

 of England, and receiving the Seine and all the small streams on the French 

 north and English south coasts, having great waterfalls at the places where are 

 now the races of Portland and the Channel Islands. This stream of water 

 or ice met the perhaps frozen Atlantic near the Scilly Islands. It requires 

 very little imagination when on these wonderful chalk cliffs to realise the 

 extensive changes that must have occurred in the glacial period, when the 

 German Ocean was obliterated, and when there was dry land to enable the 

 Spanish plants to pass over to Ireland, the plants of Brittany and the Channel 

 Islands to the south-west of England, the plants and land mollusca of Nor- 

 mandy to the south-east of England. 



The longer connection by land of Guernsey and Belgium with the east of 

 England enabled the flora and fauna of those countries to extend nearly all over 

 England and Wales ; while two-thirds of the Belgian reptiles got located in 

 England, and three or four species crossed over to Ireland on dry ground, over 

 what is now the Irish Sea. 



Then the Scandinavian plants crossed to Scotland and Wales, and a few to 

 Devonshire, remaining now in groups on the high land of Wales and Scotland. 

 Anyone familiar with the existing glaciers of Switzerland and Norway, and 

 with the lakes eroded by ice action, or with the remains of ancient glaciers in 

 Snowdonia, and with the glacier-excavated lakes there, can realise in some 

 measure the effect of the great glacial and pluvial periods, and can understand 

 that it is hopeless to attempt to explain them in a lecture-room. I cannot admit the 

 correctness of the authoritative statements in the " Principles of Geology," that 

 we must not conceive greater forces than are at present in operation, although 

 made by the eminent writer who has lately terminated a long life devoted to the 

 study of geology. The geologists present in this room to-day, however much 

 they might differ on all scientific questions, would all agree that very little is to 

 be learnt in geology or physical geography without personal observation. And 

 my advice to students is, not to rely upon books and lectures, but to use their 

 own eyes in studying the sections and drawings. 



I have now alluded to some of the points of the theory of uniform motion of 

 rivers and glaciers. I attribute to the effects of gravity in inducing friction of 

 ice upon ice, in lake and other great glaciers, enormous excavations in the ice 

 period. This closed at a date not far from the historical period in some 

 parts of Europe, while in other parts there was at the same time a pluvial 

 period, f 



* Godwin-Austin, Quart. Jour., 1850-51. 



t Mr. Croll is quite in error in stating that geologists considered the glacial period occurred 

 a million years ago : only one geologist and his followers held that opinion. Jukes, for instance, 

 in 1862 considered the glacial period quite recent. Prestwich thought that the quaternary 

 gravels were post-glacial, but he gave no estimate of such a time as Croll indicates, nor did 



