324 LIFE IN THE ALPS. 



glacier is swiftest at its centre ; that because of the 

 friction against its bed, the surface of a glacier moves 

 more rapidly than its bottom; that when the valley 

 through which the glacier moves is not straight, but 

 curved, the point of swiftest motion is shifted from its 

 centre towards the concave side of the valley. Wide 

 glaciers, moreover, are sometimes forced through narrow 

 gorges, after which they widen again. At some distance 

 below the spot where I now write is the gorge of the 

 Massa through which, in former ages, the great Aletsch 

 glacier was forced to pass, widening afterwards, and over- 

 spreading a large tract of country in its descent to the 

 valley of the Khone. All these facts hold equally good 

 for a river. 



On summer days of cloudless glory, the air is some- 

 times still, and the heat relaxing upon the mountains. 

 The glacier is then in the highest degree exhilarating. 

 Down it constantly rolls a torrent of dry tonic air, 

 which forms part of a great current of circulation. 

 From the heated valleys the light air rises, and coming 

 into contact with the higher snows, is by them chilled 

 and rendered heavier. This enables it to play the part 

 of a cataract, and to roll down the glacier to the valley 

 from which it was originally lifted by the sun. But 

 the action of the sun upon the ice itself is still more 

 impressive. Everywhere around you is heard the hum 

 of streams. Down the melting ice-slopes water trickles 

 to feed little streamlets at their bases. These meet 

 and form larger streams, which again, by their union, 

 form rivulets larger still. Water of exquisite purity 

 thus flows through channels flanked with azure crystal. 

 The water, as if rejoicing in its liberty, rushes along in 

 rapids and tumbles in sounding cascades over cliffs of 

 ice. The streams pass under frozen arches and are 

 spanned here and there by slabs of rock which, acting 



