62 STUDIES, SCIENTIFIC AND SOCIAL chap. 



originator of the modern school of glacialists, which 

 undoubtedly owes much to his energy, research, and powers 

 of exposition, though all the more important facts, as well 

 as the logical conclusions to be drawn from them, had been 

 pointed out by previous writers. 



Before proceeding further, it will be well to give a brief 

 outline of the phenomena which lead to the conclusion 

 that glaciers have formerly existed in districts and coun- 

 tries where even perpetual snow on the mountain tops is 

 now unknown. These may be briefly classed as : (1) 

 Moraines and drifts ; (2) Rounded, smoothed, or planed 

 rocks ; (3) Striae, grooves, and furrows on rock-surfaces ; 

 (4) Erratics and perched blocks. 



(1) Moraines are those heaps or ridges of rock and other 

 debris which are deposited on the surface of a glacier from 

 the precipices or mountain slopes which border it, and 

 which form what are termed lateral and medial moraines 

 while upon it, and terminal moraines when, being gradu- 

 ally discharged at its end, either from above or from 

 beneath it, they form great heaps of rock and gravel 

 corresponding in outline and extent to that of the ter- 

 minal ice-clitf. Such moraines can be seen on and near 

 all existing glaciers, and their mode of formation and 

 characteristics are perfectly well known. If the glacier is 

 continuously retreating, then the terminal moraine will 

 form more or less irregular heaps over the surface the 

 glacier has formerly covered ; but when, as is usually the 

 case, the glacier remains stationary for a considerable 

 period, then the terminal moraine will have a definite 

 form, and will often stretch quite across the valley, but 

 presenting one or more openings through which the glacier 

 stream has cut its way. Such moraines form steep mounds, 

 usually curved and often very regular, seeming from a 

 little distance to block up the valley like an artificial 

 earthwork. Among hundreds that might be enumerated 

 good examples may be seen in Glen Isla (Forfarshire), in 

 the Troutbeck valley near Windermere, and in Cwm Glas, 

 on the north side of Snowdon, this latter being so regularly 

 curved, evenly sloped, and level-topped as to look from 

 below exactly like an ancient fortification. The char- 



