THE EARTH'S SHAPE 



in fact we know it must have been, warm enough once to 

 encourage and support what resembled a tropical vegeta- 

 tion. It must also have been at one time as cold as 

 Siberia in the winter. 



Therefore we should expect to find, if we digged down 

 in the earth, or in any portion of the earth which had 

 undergone these changes, some traces of them. For 

 example, if at one time the sea covered England for 

 thousands or hundreds of thousands of years, de- 

 positing the remains of millions of animals on the sea's 

 bottom during that period, we should expect to find some 

 traces of these remains perhaps in the form of chalk, 

 seeing that the bones and shells of fishes dwelling in the 

 sea contain a good deal of lime. Or again, if a forest 

 covered England and grew and decayed there, not merely 

 for a period like that which has elapsed since the Romans 

 first set foot in Britain, but for a hundred times as long, 

 we should expect to find some sort of vegetable deposit, 

 hardened most probably by other layers above it. Do we ? 

 Well, coal is a vegetable deposit. If there was a time 

 when ice covered the land we should expect to find traces 

 of that ; if a time when the land was desert ; or when it 

 was a lake each and every one of these periods ought to 

 leave some remains, some epitaph of itself. So they do. 



Let us for a moment consider with Sir Archibald 

 Geikie 1 the subsoil beneath cities that have been in- 

 habited for many centuries. In London, for example, 

 when excavations are made for drainage, building, and 

 other purposes, there are sometimes found, many feet 

 1 Sir Archibald Geikie's Introduction to Geology. 

 34 



