72 TOWN GEOLOGY. [in. 



at least soon after, the sandstones or marls on which it 

 lies ; that as soon as the one had settled at the bottom 

 of some old sea, the other settled on the top of it, in 

 the same sea. 



A fair and reasonable guess, which would in many 

 cases, indeed in most, be quite true. But in this case 

 it would be a mistake. The sandstone and marls are 

 immensely older than the boulder-clay. They are, 

 humanly speaking, some four or five worlds older. 



What do I mean ? This that between the time 

 when the one, and the time when the other, was made, 

 the British Islands, and probably the whole continent 

 of Europe, have changed four or five times ; in shape ; 

 in height above the sea, or depth below it ; in climate ; 

 in the kinds of plants and animals which have dwelt on 

 them, or on their sea-bottoms. And surely it is not 

 too strong a metaphor, to call such changes a change 

 from an old world to a new one. 



Mind. I do not say that these changes were sudden 

 or violent. It is far more probable that they are only 

 part and parcel of that vast but slow change which is 

 going on everywhere over our whole globe. I think 

 that will appear probable in the course of this paper- 

 But that these changes have taken place, is my main 

 thesis. The fact I assert ; and I am bound to try and 

 prove it. And in trying to do so, I shall no longer 

 treat my readers, as I did in the first two papers, like 

 children. I shall take for granted that they now 

 understand something of the method by which geolo- 

 gical problems are worked out ; and can trust it, and 

 me ; and shall state boldly the conclusions of geolo- 

 gists, only giving proof where proof is specially needed. 



Now you must understand that in England there 



