136 Mr iMurchibOii on the Glacial Theory. 



tains behind it, the tops of which, as seen from the mast-heads, were esti- 

 mated to be a degree of latitude to the soutli of the sea-face of this great 

 wall of ice, at not more than half a mile from which the soundhigs were at 

 318 fathoms deep, and upon a bed of blue soft mud. Here, then, the geo- 

 logist is presented 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 striae and polish on their 

 surface, and the wide dispersion of blocks and detritus, are supposed to 

 have been affected by former terrestrial glacial action. Whilst, however, 

 we have here the proof that existing glaciers advance 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 extended 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 mountains against which they rested. By the. same reasoning we 

 may infer that the striae and polish of rocks, or accumulation 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 centres of congelation. 



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

 serve to explain most of our ancient phenomena, it has been shewn 

 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 fea- 

 tures under which the existing agency of ice may be viewed apart from the 

 results of the movements of glaciers. More than enough has indeed 

 already been said; for so long as the greater number of practical geo- 

 logists of Europe are opposed to the wide extension of a terrestrial 

 glacial theory, there can be little risk that such doctrine 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 Hitchcock of the United States. In North Ame- 

 rica, striated, scored, and polished surfaces of rocks, proceeding from N. to 

 S. for vast distances, 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 phcno- 

 tnena and the accumulations of gravel and blocks had always been in- 



* Geological Procee<3ing?, Murchiwn ami De N erneuil on Russia, vol. iii. 

 p. 400; 



