lid Piofessor Hiigi's Ob^crvutions on the 



jecting this idea, Mr Hugi delivers some interesting details re- 

 garding the melting of the glaciers, which we may now mention. 

 " The fact,"" says he, " that the glaciers of the two kinds melt 

 only at the lower surface, is a truth universally acknowledged, 

 and concerning which no doubt exists; but it has been erro- 

 neously maintained, that in winter the glacier is attached or 

 fixed to the soil by congelation. The progressive move- 

 ment of glaciers during winter would alone suffice to nega- 

 tive this assertion, if the observation of the fact itself, and that 

 of the heat of the soil at this depth, did not contradict it. It 

 is proper to remark, that the nature and bearing of the 

 strata of the mountain on which the glacier rests have a very 

 great influence on the melting of the lower surface. Among the 

 glaciers of the Uraz and of the Aar (superior") of Viesch and 

 Gastern, I have succeeded in penetrating to a considerable depth 

 below the mass of ice. Wherever a solid connected mass of 

 rock was visible, the glacier rested securely upon it ; the base of 

 the glacier melted, when by the general progressive movement 

 it had quitted the rock to descend upon the debris. The deeper 

 and more solidly based the rqck was, the larger were the bases 

 of the glacier. Currents of warm aii' were observed issuing from 

 the depths of the earth. But an observation which has surprised 

 me more, and which I have often repeated, is, that during the 

 day the temperature under the glacier was always a half lower 

 than above, and that though the lower melted ten times more than 

 the upper surface. Perhaps this difference is owing to this, that 

 it is exposed each night to a fresh congelation, whilst the other is 

 constantly exposed to a temperature a little above 32° Fahr. It 

 may fiu'ther probablv be attributed to the action of the currents of 

 air wliich pass from the bottom of the ravine to the surface, to re- 

 establish the equilibrium; but observations'are wanting on the last 

 point. The fact is, that there exists under the glaciers an extra- 

 ordinary humidity, by which they are moistened without receiv- 

 ing even a single drop of water. On the contrary, there exists 

 at the upper a singular aridity, in consequence of which the ice 

 tends to evaporate, and also to exhibit asperities and cavities. 

 It rarely happens that the sun's rays act so powerfully on the 

 glacier as to form accumulations of water on its surface. The 

 streamlets of the glaciers generally proceed from newly fallen 



