764 



GEOLOGY. 



a a Divisions of the Strata. 

 b b Strise. 



and difficult problems of geology ; nor has any theory yet been proposed offering a 

 solution of it which is perfectly satisfactory. Some reasons have already been assigned 

 for rejecting the long prevalent opinion that these phenomena resulted from the deluge 



of Noah; namely, the presence of animals 

 of extinct species, and some of extinct ge- 

 nera in the drift, with the absence of the 

 remains of human beings, and of all vestiges 

 of the arts and operations of man ; and, in 

 addition, it may be remarked, that if that 

 event was local, confined to a part of south- 

 western Asia, as we have previously argued, 

 it is further inadmissible as an explanation 

 of effects certainly common to the whole 

 northern hemisphere, and to the southern 

 extremities of America. But the single consideration that the vast masses of gravel and 

 blocks strewed over such extensive areas, do not belong to one violent and transitory 

 period, but have been aggregated at different epochs, by causes sometimes operating 

 feebly and slowly, and at other times violently and powerfully the evidence of which 

 is irresistible to those who have studied the subject is amply sufficient by itself to 

 disprove the idea of these accumulations being the consequence of the transient flood 

 recorded in the sacred history. 



It would require a volume to detail and discuss the various views of scientific inquirers 

 respecting the drift deposits. An outline of the principal theories will suffice. 1. The 

 sudden elevation of chains of mountains, while yet wholly or in part beneath the waters, 

 which, rushing away from the axis of elevation, would transport detritus and blocks in 

 various directions, has been suggested to account for the phenomena. The Alps have 

 been referred to, as supplying some evidence in favour of this view. They appear to 

 have been upheaved, if not from the ocean, yet to a considerable height, after the 

 deposition of the tertiary strata, for patches of these strata are found capping their 

 summits, and lying in their mountain valleys, while the drift is scattered in all directions 

 from the central axis, on the Jura range, and on the plains of Lombardy. It is very 

 likely that this has been influential in the production of drift ; but though the paroxysmal 

 elevation of a mountain chain from submergence would cause the waters to rush away 

 violently from it, sweeping along a vast amount of detritus, yet a sudden and transient 

 rush is inadequate to the effect, which in many instances evinces the action of a 

 disturbing cause for a considerable length of time. 2. Strong currents, waves, and 

 tides of the ocean, bearing icebergs upon their bosom, while the districts covered with 

 far-borne detritus and blocks were beneath the sea, have been proposed to explain their 

 accumulation upon them, the districts being subsequently elevated. This theory has 

 evidence in its favour, for in a former section we have noticed the transporting power 

 of icebergs with reference to the solid materials of the land ; and it admits not of a doubt, 

 that if the floor of the north Atlantic were now laid bare, we should see its surface 

 covered with erratic blocks borne thither by the icy masses which annually melt away in 

 its waters, derived from the shores of Greenland and Spitzbergen. But this can only 

 be admitted as explaining part of the case, for it can scarcely apply to the drift con- 

 taining the bones of the elephant and mastodon, with the other terrestrial quadrupeds. 

 3. It has been conceived that a powerful and extensive subaqueous elevation took place 

 the arctic regions, driving the northern ocean southward, over Great Britain, the 

 north of Europe and America, bearing along masses of ice, blocks, and detritus ; and 

 that this vertical movement of the bed of the polar deep transpired repeatedly, product 



