M. A. de la Rive on Glaciers. 107 



liois^ had risen laterally against a neighbouring mountain, 

 designated the Chapeau^ which it enclosed on its northern 

 aspect, threatening to make inaccessible a spot which is often 

 visited by the curious traveller who visits Charaouni. During 

 the spring of the year 1818, although the winter had been 

 much more mild than severe, the glaciers had not ceased to 

 advance, especially at their lower portions, in a way w^hich 

 alarmed the occupiers of the nearest dwellings ; and this 

 phenomenon occurred also at the glaciers both of the Tyrol 

 and at those of Chamouni. Far, however, from continuing 

 their progressive advance, in the following year, all these 

 glaciers, after having undergone a process of arrest, actually 

 retrograded to an extent which could not be mistaken, and 

 resumed their ordinary dimensions, at all points; as prolonged 

 observation teaches us to expect. The extension and the suc- 

 ceeding retreat depended upon this, — that the years 1816 and 

 1817, after having been extraordinary years, in respect of 

 the enormous quantity of rain and snow which fell, had been 

 followed by seasons which were rather dry than wet, or which, 

 at least, were below the average, as to the quantity of rain. 

 And, if the occurrence of two consecutive years more humid 

 than ordinary sufficed to produce such a vast increase of the 

 existing glaciers, it is not difficult to comprehend, that if a 

 certain number of similar years had succeeded each other 

 without interruption, then the glaciers of Chamouni, filling 

 up the valley of the Arve, would have advanced, and finally 

 would have penetrated to the valley of the Rhone. In fact, 

 in circumstances analogous to those which produced the two 

 consecutive years of 1816 and 1817, all we may say that is 

 desiderated, so far as the mountains which produced them 

 are concerned, is, that winters should regularly succeed each 

 other, and without intermediate summers ; this result then 

 would follow, that the accumulations of snow would soon 

 become so enormous as to produce a most rapid progressive 

 advance of glaciers descending from their summits. 



After having thus explained the appearance and produc- 

 tion of great glaciers, let us now consider how we may 

 account for their disappearance. At the first glance it ap- 

 pears that the enormous humidity which had accompanied 



