ii.] THE PEBBLES IN THE STREET. 65 



tude 70, far within the Arctic circle. Now there 

 certain strata of rock, older than the ice, have not been 

 destroyed by the grinding of the ice-cap ; and they 

 are full of fossil plants. But of what kind of plants ? 

 Of the same families as now grow in the warmer parts 

 of the United States. Even a tulip-tree has been 

 found among them. Now how is this to be explained ? 



Either we must say that the climate of Greenland 

 was then so much warmer than now, that it had sum- 

 mers probably as hot as those of New York ; or we 

 must say that these leaves and stems were floated 

 thither from the United States. But if we say the 

 latter, we must allow a change in the shape of the 

 land which is enormous. For nothing now can float 

 northward from the United States into Baffin's Bay. 

 The polar current sets out of Baffin's Bay southward, 

 bringing icebergs down, not leaves up, through Davis's 

 Straits. And in any case we must allow that the hills 

 of Disco Island were then the bottom of a sea : or 

 how would the leaves have been deposited in them 

 at all ? 



So much for the change of climate and land which 

 can be proved to have gone on in Greenland. It has 

 become colder. Why should it not some day become 

 warmer again ? 



Now for England. It can be proved, as far as 

 common sense can prove anything, that England was, 

 before the age of ice, much warmer than it is now, 

 and grew gradually cooler and cooler, just as, while 

 the age of ice was dying out, it grew warmer again. 



Now what proof is there of that ? 



This. Underneath London as, I dare say, many 

 of you know there lies four or five hundred feet of 

 sc. F 



