6 



THE GEOLOGIST. 



we learn that the snow which forms the glacial mass is not 

 dej^osited in situ (witness the verdant patches of ground 

 alluded to_, enclosed by walls of ice) and that the snow of which 

 the glaciers are formed is precisely the same in character as 

 that which has been observed to fall at great altitudes. The 

 effect of variations of temperature must be apparent, and 

 therefore we will not allude to this subject ; but when, in 

 addition to the natural thaw produced by heat, we may add 

 the occurrence of rain at these elevations, we may easily con- 

 ceive the mass of snow to become saturated, as stated by 

 Hugi, and subsequently to become congealed on the return 

 of frost, and hence the appearance which the glaciers 

 present. 



The observations of all travellers confirm the opinion, 

 " that elevated districts are those in which snow is most 

 frequent,^^ the degrees being regulated by the altitudes. It 

 is also natural to suppose, that when rain or thawing occurs, 

 the lowest situate portions of the glacial mass would first 

 become saturated, which is proved by the difference observed 

 in the ice in the various regions ; thus, the ice which occurs 

 in the most elevated districts is compact and transparent, 

 more closely resembling that which is formed by the con- 

 gelation of water, than the ice forming the glaciers, which, 

 as we have seen, is derived from congealed snow. These 

 causes would tend to retain the snow, in elevated districts, 

 more or less dry, and whilst producing this effect, would 

 also diminish the retentive or binding quahty which it would 

 otherwise possess, and on this account any superabundance 

 of snow which might fall, would slip from those situations, 

 and would naturally follow the inclinations of the country as 

 their course. 



Having traced their origin, we will next consider their 

 action and effects, a subject which presents a wider field for 

 observation and inquiry. 



