Williams : Louis Agassiz. 



the reach, now-a-days, of the agencies to which they must have been 

 at one time and long subjected. 



Although we all know what glaciers are, I will mention, for the sake 

 of clearness and completeness, that the name is given to those masses 

 of ice which are found, in all elevated latitudes, clothing the mountain 

 tops, and clogging up the higher valleys. At the present day such 

 phenomena as glaciers are, of course, to be observed only in those 

 situations called alpine, or peculiarly hilly ; though a single mount of 

 great height, like Mount Etna, presents so far the glaciers with their 

 usual peculiarities. However, it is not only where they now exist that 

 their action is discoverable. They have left their marks over almost the 

 whole globe, or at least over all the northern countries of Europe — 

 warm, mild, or chilly ; and so they have led to the certainty that 

 immense changes have occurred in respect to the temperature of such 

 parts of the earth. By the presence of blocks of stone in quarters to 

 which they are by nature strangers, and where they lie alone to 

 excite wonder, as also, by the existence of shells where shells never could 

 have been found without some such means of transportation, and 

 by the presence of the remains of plants foreign to the soil, the action 

 of glaciers is proved in. climes where they have been h^ng, long 

 unknown. Nor must it be imagined that these transportations have gone 

 on merely on a small scale, or but from one to another hill- side. On the 

 contrary, for example, the granite cliff of Criffel, a large hill in Kirk- 

 cudbrightshire, has been found strewn on the English shores of the 

 Solway, and shifted masses of Norwegian stone have been discovered on 

 the eastern coasts of Britain. The alteration of temperature, and other 

 circumstances, must thus have been vast, as far as the lands in 

 question were concerned ; and the glacial theory assumes a degree of 

 importance of no ordinary kind in the eyes of all to whom the history 

 of the earth is interesting. 



It was, in the first instance, by observing glacial phenomena on a 

 comparatively small scale, or as they exist now, that Agassiz came to 

 the conclusions on which he based his great theory. His earliest 

 observations were made in his own alpine country, adjoining Neuf- 

 chatel. The huge glaciers there discoverable may be poetically called 



eternal," but they are still subject to change. The texture of their 

 component ice is not solid, but spongy, or, at least, penetrated by 

 chinks and pores. When the heats of summer occur, they partially 

 affect these icy masses, and the water sinks naturally into such 

 vacuities. This water as naturally freezes in the winter season, and 

 in freezing, expands, causing a general dilatation of the glacier con- 



