27 



The ice which had melted back a bit in the Summer advanced 

 again in the Winter. The retreat caused by a few mild seasons 

 may have been counterbalanced by a few succeeding severe ones. 

 I should not be surprised if it took the ice a century or two to say 

 farewell There is evidence all around us relating to these 

 matters, but the reading of it is a task of pecnlar difficulty. But, 

 at length the ice moved off, and must have left the suiface of our 

 neighbourhood in a dirty mess. The surfaces of our higher 

 moors were not ploughed by ice rivers, but much ice and snow 

 must have collected on them, and it is doubtful whether there 

 would be much vegetation clothing them when the ice-age came 

 to an end. The lowland tract would consist of muddy expanses 

 with boulders of all sizes here and there, and numberless little 

 tarns scattered over its surface. Life would gradually find its 

 way back. Some life there would be indeed, all along, Bears and 

 a few other animals and some birds would be there, but now from 

 the droppings of birds would begin to spring a varied vegetation. 

 Seeds would come floating in the wind, or adhering to the bodies 

 of animals. Ducks would come to the little tarns, and to their 

 webbed feet there might be sticking little pond snails, which they 

 had brought from a hundred miles away, and the pond so visited 

 might thereby become in a short time filled with snail-life to 

 furnish food for wild ducks for centuries to come. I have lately 

 made some investigation into the process of filling up one of 

 these glacial tarns of Kildale. 



I have already remarked " there is a world of interest involved 

 in the tracing of pre-glacial river courses," but, I stated that I 

 could not then stop to speak of them. I had said there was 

 reason to believe that the chalk sea bad extended over Cleveland 

 right up to the Pennines. Well, when the land was raised above 

 sea-level after the age of the chalk, there was a gradual slope 

 from the crest of the Pennines to the Eastward, and a series of 

 rivers would be initiated flowing downwards, according to the dip 

 of the beds. Such rivers are called " consequent " rivers. The 

 upper portion of some of these consequent rivers probably 

 survive to-day in pretty much their original position as the Wear, 

 Tees, Swale, Ure, Nidd, Wharfe, Aire, Calder. These rivers, in 

 all probability, flowed right down to the East Coast. The Ouse, 

 a " subsequent," tributary of the original Aire Humber, working 

 back among the soft strata of the Triassic Valley, has captured 

 many of these rivers, and the Tees and Wear have been captured 

 by " subsequents " working from the other end of the valley. 

 What course then did these rivers originally follow '? It is easy to 

 race the Ure through the Gilling Gap to the Coast near Filey. I 



