Correspondence — Prof. Edward Hull. 189 



COEEESPOUDEUCE. 



THE GEOLOGICAL AGE OF THE NORTH ATLANTIC OCEAN.— EEPLT 

 OF PROFESSOR HULL TO PROFESSOR LE CONTE. 



Sir, — I have read with much pleasure Professor Le Conte's views 

 on the question of the " Permanence of Continents and Ocean- 

 Basins " ; and especially with reference to the growth of the North 

 American Continent. 1 I am glad that he does not cany his views 

 as far as some geologists on this question. As stated, they are 

 substantially the same as those supported in his " Elements of 

 Geology" (Edit. 1885). It seems to me, however, that Prof. Le 

 Conte scarcely realizes sufficiently what must have been the effect 

 of continued subsidence during the whole of the Palaeozoic period 

 in extending the sea-area, and consequently in pushing the ad- 

 joining land-area further into that of the present North Atlantic 

 Ocean. In his ideal-section (Elem. p. 288) of the Paleozoic rocks 

 from the Primordial downwards to the Carboniferous, which is 

 consistent with his statement that the whole of these rocks in the 

 United States are conformable, Prof. Le Conte makes it clear that 

 were these strata reduced to the original horizontal position, there 

 would be several thousand feet of marine sediments, which must 

 originally have overlapped on the flanks of the lands formed of 

 Archaean rocks. This will, probably, explain to him why in my 

 sketch-map No. 2 I have carried the northern part of the continental 

 border westward so as to cut through Labrador, not in "Primordial 

 times," as he supposes, but in Silurian times, when the land-area 

 was further depressed. 2 



I am gratified to find that on the question of the position of the 

 and and sea areas during Archaean (or Laurentian) times Prof. Le 

 Conte is in accord with myself ; on the other hand I fully agree with 

 him as to the immense duration of the " Lost Interval " which 

 elapsed between the Archaean and Primordial eras, and the extent of 

 the denudation of the raised sea-beds over the American and European 

 continents. But, I cannot concur with him in supposing that the 

 small tracts of land which were (at least partially) maintained in 

 the North, as the Laurentian " Nucleus," or along the East of the 

 Appalachians (even with a considerable margin including some now 

 ocean-covered tracts), were sufficient to supply the amount of Palaeo- 

 zoic sediment, which, when originally deposited (i.e. before denudation), 

 was the measure of the denudation of these tracts themselves. The 

 conformable relations of these beds throughout a vertical depth of 

 several thousands of feet imperatively involves the view of the con- 

 temporaneous existence of an extensive continental area, stretching 

 both to the north and east of the present margins of the Silurian 

 strata. Nor, as it appears to me, does Prof. Le Conte recognize 

 sufficiently (if at all) the significance, in reference to this question, 

 of that on which I have laid principal stress in my essay ; namely, 



1 Geological Magazine, March, 18S6. p. 97. 



2 Scient. Trans. Roy. Dublin Soc. vol. iii. new ser. plate vii. p. 319. 



