216 THE PHENOMENA OF DRIFT, OR 



generally have a northerly and southerly, or northwesterly and 

 southeasterly dkection, showing that the icebergs and currents 

 came from that direction ? I am unable, I confess, to conceive 

 how our phenomena of drift can be explained, 'without suppos- 

 ing nearly the entire surface beneath the waters when they were 

 produced ; and that the work was accomplished nearly at the 

 same time, — that is, within a few centuries, or thousands of 

 years, — at aU altitudes. 



If it be said that particular mountains may have been raised, like 

 the Alps, from the ocean, since the period when glacio-aqueous 

 agency commenced, while, as a whole, the continent has been 

 raised but slightly, I reply that such an event could not have 

 taken place without producing local disturbances in the moraines, 

 and among the striated and embossed rocks, around such moun- 

 tains ; as has been the case in the drift of the Alps : and that as yet 

 no example of such disturbance has been pointed out. Every care- 

 ful observer of these phenomena, it appears to me, will come to 

 the conclusion, whatever be his theoretical views, that if this 

 continent has been recently elevated, it must have been as a 

 whole ; and that the relative levels of the surface have not been 

 altered, since the glacio-aqueous period, to any great extent. 



These are certainly very strong objections to this iceberg the- 

 ory of drift. I admire the theory, however, and should prefer it 

 to all others, if these objections can be removed. Another 

 theory advocated by M. De la Beche, supposes the contents of 

 the northern ocean, aqueous and glacial, to have been precipitated 

 over the countries further south, by the elevation of the regions 

 around the pole. This theory avoids the difficulties connected 

 with the vertical movements of our continent, by fmiiishing an 

 ocean to cover it at its present level. It fm'nishes also the requi- 

 site icebergs, without a previous change of climate, and a cause 

 for the glacial period, which prevailed during the accumulation 

 of drift. Applied to the low countries of northern Evirope and 

 Asia, it may be adequate to the effects. But on this continent 

 we want an ocean to rise six thousand feet above the present sea 

 level, and the southerly currents in it to continue at least for cen- 

 turies, to produce all the erosions clearly referable to.glacio- 



