400 THE CANADIAN NATURALIST. [Oct. 



in those valleys where the sources of the Indus rise, between the 

 latitudes 35° and 36^ N. The highest peaks of the Karakorum 

 rang-, attain in that region an elevation of 28,000 feet above the 

 sea. The ghiciers, says Captain Austen, have been advancing, 

 within the memory of the living inhabitants, so as greatly to en- 

 croach on the cultivated lands, and have so altered the climate of 

 adjoining valleys immediately below, that only one crop a year can 

 now be reaped from fields which formerly yielded two crops. If 

 such changes can be experienced in less than a century, without 

 any perceptible modification in the physical geography of that part 

 of Asia, what mighty effects may we not imagine the submergence 

 of the Sahara to have produced in adding to the size of the iVlpine 

 glaciers? If, between the years 1812 and 1820, a mere diminu- 

 tion of the number of days during which the sirocco blew could so 

 much promote the growth and onward movement of the ice, how 

 much greater a change would result from the total cessation of the 

 same wind ! But this would give no idea of what must have hap- 

 pened in the glacial period ; for we cannot suppose the action of the 

 south wind to have been suspended ; it was not in abeyance, but its 

 character was entirely different, and of an opposite nature, under 

 the altered geographical conditions above contemplated. First, 

 instead of passing over a parched and scorching desert, between the 

 twentieth and thirty-fifth parallels of latitude, it would plentifully 

 absorb moisture from a sea many hundreds of miles wide, Next^ 

 in its course over the Mediterranean, it would take up still more 

 aqueous vapor ; and when, after complete saturation, it struck the 

 Alps, it would be driven up into the higher and more rarified 

 regions of the atmosphere. There the aerial current, as fast as it 

 was cooled, would discharge its aqueous burden in the form of 

 snow, so that the same wind which is now called " the devourer 

 of ice" would become its principal feeder. 



If we thus embrace Escher's theory, as accounting in no small 

 degree for the vast size of the extinct ci'laciers of Switzerland and 

 Northern Italy, we are by no means debarred from accepting at 

 the same time L'harpentier's suggestion, that the Alps in the 

 glacial period were 2000 or 3000 feet higher than they are now. 

 Such a difference in altitude may have been an auxiliary cause of 

 the extreme cold, and seems the more probable now that we have 

 obtained unequivocal proofs of such great oscillations of level in 

 Wales within the period under consideration. We may also avail 

 ourselves of another source of refrigeration which may have coin- 



