Other Glaciers, 375 



evidence that the present glaciers were once on an 

 immensely larger scale than at present. The proof not 

 only lies in the polished and grooved rocks far removed 

 from the actual glaciers of the present day, but also in 

 numerous moraines on a scale so immense that the 

 largest now forming in the Alps are of pigmy size when 

 compared with them. Such a moraine is the great one 

 of the Dora Baltea, sometimes called the Moraine of 

 Ivrea, which, on the plains outside the mouth of the 

 Val d'Aosta, encloses a circuit of about sixty miles, and 

 rises above the plain more than 1,600 feet in height, 

 being altogether formed of mere accumulations of 

 moraine rubbish. Its width in places averages about 

 seven miles, as mapped by Grastaldi. Many others 

 might be cited. The same kind of phenomena occur in 

 the Altai Mountains, the Himalayah, the Caucasus, the 

 Eocky Mountains, the Andes, the Sierra Nevada, and 

 the Pyrenees of Spain, the Atlas of Morocco, the moun- 

 tains of Sweden and Norway, the Black Forest and the 

 Vosges, and in many other northern mountain chains or 

 clusters, great or small, that have been critically ex- 

 amined. In the southern hemisphere, where mountain 

 ranges are comparatively scarce, the same ancient exten- 

 sion of glaciers is prominent in New Zealand. There- 

 fore there can be no doubt that at late periods of the 

 world's history a climate or climates prevailed over large 

 tracts of the earth's surface generally, but not always, 

 of extreme arctic severity, for there were intermittent 

 episodes of comparative warmth, when what is misnamed 

 perpetual snow disappeared, or almost disappeared from 

 mountain regions of moderate height. The cold of these 

 minor cycles in time (for as shown by Dr. Croll, glacial 

 cycles alternate in the northern and southern hemi- 

 spheres) was produced by causes about which there have 



