590 Geological Society'. Anniversary Address, 184:2. 



than half a mile from which the soundings were at 318 fathoms deep, 

 and upon a bed of blue soft mud. Here then the geologist is pre- 

 sented with abundant matter for speculation. Volcanos in the midst 

 of eternal polar snow and glaciers, with seaward faces as wide as 

 some of the continental tracts, which, from the striaj and polish on 

 their surface, and the wide dispersion of blocks and detritus, are sup- 

 posed to have been affected by former terrestrial glacial action. 

 Whilst, however, we have here the proof that existing glaciers ad- 

 vance some few miles into the sea, we are also informed that the ice 

 ceases suddenly against an ocean 2000 feet deep, and thus we are 

 led to conclude that many glaciers, which may formerly have extend- 

 ed themselves into the sea, had a length, the extent of which, whether 

 like this antarctic example, or those which have been measured 

 in the Alps, was proportioned to the altitude of the ancient moun- 

 tains against which they rested. By the same reasoning we may 

 infer that the striaj and polish of rocks, or accumidation of coarse 

 detritus, and large blocks which are only to be observed in places 

 far beyond the limits that are now established between mountains 

 and their dependent masses of ice, cannot be due to the advance of 

 former solid glaciers, but must rather be referred, as I have argued, 

 to the floating away of vast packs and icebergs liberated from ceti- 

 tres of congelation. 



But besides the submarine operations now in action, and which may 

 serve to explain most of our ancient phajnomena, it has been shown 

 that in Russia and other cold countries there are several actual sub- 

 aerial processes, by which large blocks are accumulated at different 

 heights by the expansion of the ice of rivers, or have been piled up 

 by the glacial action of former lakes, when at much higher levels *, 

 leaving lines of coarse angular blocks. 



I desist, however, in this place from entering further into the many 

 features under which the existing agency of ice may be viewed apart 

 from the results of the movements of glaqjers. More than enough 

 has indeed already been said : for so long as the greater number 

 of practical geologists of Europe are opposed to the wide extension 

 of a terrestrial glacial theory, there can be little risk that such doc- 

 trine should take too deep a hold of the mind. But whilst we may 

 have no fear of this sort in Europe, I have lately read with regret 

 certain passages in the Anniversary Discourse of Professor Hitch- 

 cock of the United States. In North America, striated, scored, and 

 polished surfaces of rocks, proceeding from N. to S. for vast di- 

 stances, occupy, it appears, at intervals a breadth of 2000 miles, and 

 are seen on hard rocks at all levels from the sea-shore to heights 

 of 3000 and 4000 feet. Professor Hitchcock tells us, that these 

 phcfinomena and the accumulations of gravel and blocks had always 

 been inexplicable, until the work of Agassiz unexpectedly threw a 

 flood of light upon his mindf. If Professor Hitchcock could de- 



• Geological Proceedings, Murchison and De Verneuil on Russia, vol. 

 iii. p. 406. [Phil. Mag., vol. xix., p. 489-] 



t Anniversary Address. Philadelphia, April 1841, p. 24. I must be 

 excused for stating that Professor Hitchcock has entirely misconceived my 



