22 THE PRINCIPLES OF 



that Sir Charles Lyell, in speaking upon the spherical form 

 of our globe and the reason why it possesses its present shape, 

 does not hesitate to say that, if the globe had originally been 

 turned out angular or cubic, the action of water alone would 

 in process of time have worn down its angles, and the rotary 

 action would itself have so distributed the worn materials that 

 it would at length have taken the form which it now presents. 

 Neither must we omit glacial action. If we consult 

 Professor Geikie's excellent treatise we shall find, in reference 

 to soil, that he dismisses the subject by attributing the loose 

 matter which covers the surface in a great measure to glacial 

 action. So powerful is this agency that it might well be 

 accredited with the process of soil formation. It is a geo- 

 logical fact, that the whole of Europe and our own country 

 were at some distant period covered with ice, just as we see 

 the Polar regions and Greenland covered with immense 

 thicknesses of ice at the present day. Those who have 

 studied glacial action know well that a glacier moves. A 

 glacier is not stationary, but there is a slow movement where 

 the nature of the ground admits of it a slow downward 

 movement. Ice is plastic. The particles move one upon 

 another, slowly, but surely. This flowing of the glacier is 

 carried down to the bottom, and the consequence is that 

 the glacier grinds .the rocky surface upon which it rests, 

 absolutely scarifying it, absolutely tilling it, if we may so 

 speak, causing great grooves in the direction of the move- 

 ment. We can still find upon our hills the strice or striated 

 marks of glacial action ; and those of us who have had the 

 good fortune to have stood upon a glacier and to have watched 

 it, will have noticed that from its tail, or lowest point, issues 

 perpetually a milky stream, the milkiness or turbidity being 

 simply caused by rocky material which the glacial action has 

 forcibly worn, pounded, and grated ; and this material, sus- 

 pended in the waters of the melting glacier, is carried down 



