,g,,. THE PERMANENCE OF CONTINENTS. 739 



times. The Orinoco was tlien in existence, but brought no 

 appreciable sediment so far from what was then the mouth of the 

 river. 



The Orinoco seems, therefore, to have discharged its sediment 

 into a land-locked sea greatly resembling the existing Gulf of Mexico. 

 If Mr. Guppy's account of the geology be correct, the estuary of the 

 ■Orinoco and the Gulf of Paria ought, on the theory adopted by Mr. 

 McGee, to ha\'e formed a subsiding area ever since early Tertiary 

 times, for it is over that area that the sediment has been deposited. 

 Such may have been the case, though we have as yet no direct 

 evidence of the fact. When, however, we read that the southern half 

 of Trinidad is occupied by deposits formed at the great depth of 1,000 

 fathoms, while the northern half has never been submerged since 

 Palaeozoic times, it is not easy to reconcile this rise of the sea-bottom 

 with Mr. McGee's theory. 



The views of Messrs. McGee and Guppy, as we remarked, have 

 only quite lately been propounded. If we refer to literature a little 

 ■earlier, however, there are numerous papers by other authors with a 

 •direct bearing on the same subject ; and we may allude especially to 

 four papers by Professor James D. Dana,' in which the permanence of 

 the continental area of North America since the beginning of Palaeozoic 

 times, at least, seems to be satisfactorily proved. " The facts illus- 

 trate strikingly the great truth that the earth's features, even to many 

 minor details, were defined in Archaean time, and, consequently, that 

 Archaean conditions exercised a special and even detailed control 

 ■over future continental growth. The extension of North America to 

 the most eastern point of Newfoundland, and beyond it, was deter- 

 mined in this beginning time ; and likewise, that of the European 

 Continent to the Hebrides, in front of the Scandinavian Archaean 

 area." The main result is briefly summed up by Professor Dana in 

 the following letter, while Dr. Blanford and Mr. Jukes-Browne add 

 some further comments from their point of view. 



II. 



With regard to the discussion on- the Permanence of Oceans and 

 ■Continents now proceeding in Natural Science, I may say that the 

 argument from North America is brief: that the successive formations, 

 from the Archaean onward, follow one another quite regularly over the 

 surface that lies outside of the northern Archaean area, and bear 



1 " Areas of Continental Progress in North America, and the Influence of the 

 'Conditions of these Areas on the work carried forward within them," Bull. Geol. Soc. 

 America, vol. i., i88g, pp. 36-48. 



"Archaean Axes of Eastern North America," Aiiier. jfouin. Set., vol. xxxix., 

 pp. 378-383. 1890. 



" Rocky Mountain Protaxis and the Post-Cretaceous Mountain-makmg along 

 dts Course," ibul., vol. xl., pp. 181-196, 1890. 



"On Subdivisions in Archaean History," ibid., vol. xliii., pp. 455-462, 1892. 



