VoL 57.] PHYSICAL DEVELOPAIE^fT OF ST. KITTS, ETC. 543 



"but the amounts vary somewhat in the different groups of islands, 

 as also the character of the evidence. Thus, in this group, the 

 floor of the sunken plains was nowhere seen lifted to the surface 

 by the general changes of level, as in other islands. The elevation 

 of the area, so far as can be discovered, is in no way dependent 

 upon the volcanic forces outside of the districts occupied by such 

 ridges. The various groups of islands, now partly drowned, so as 

 to constitute the banks, are the surfaces of tablelands, in part 

 surmounted by mountains, which rise conspicuously above the floor 

 of the Antillean plateau. They were not raised into prominence 

 by eruptive forces beyond the limits of the volcanic ridges them- 

 selves. On the other hand, the slopes or escarpments bounding 

 them are everywhere marked by excavations, indicating the intense 

 atmospheric erosion to which they were long subjected. 



Discussion (on the pour preceding Papers). 



Prof. Hull having expressed his thanks to Prof. Watts for the 

 able manner in which he had prepared the printed abstracts of the 

 papers, and, in the absence of the Author, communicated their contents 

 to the meeting, said it would be evident that the Fellows had before 

 them the results of great labour, extending over several years, and 

 following up the results communicated to the world in the remarkable 

 memoir on ' The Eeconstruction of the Antillean Continent.' The 

 results of the Author's investigations in all the islands described were 

 in general agreement with each other — showing that the islands 

 themselves were but the higher unsubmerged summits of a con- 

 tinental plateau which once extended, during a period of high 

 elevation, from South to North America, and had undergone several 

 oscillations of level, the most important being the elevatory move- 

 ment at the close of the Pliocene Period, amounting to over 3000 feet, 

 which gave opportunity for the migration of Elephas from the 

 continent to the Island of Guadeloupe, and for the large rodents (de- 

 scribed by Cope) to enter the region now constituting the Island of 

 St. Martin. It seemed to him that this great elevatory movement, 

 evidenced by the existence of the submerged river-channels, had its 

 counterpart along the eastern borders of the Atlantic, as shown by 

 the submerged river-channels of the British Isles, Western Europe, 

 and the Congo. In conclusion, he desired to join in thanking the 

 Author for his communication to the Society. 



Prof. SoLLAS, in commenting on the four papers of the Author, 

 which were really one, and might conveniently be collected together as 

 dealing with the geology of the Windward Isles, remarked that, with 

 regard to the great submergence imagined by the Author, it appeared 

 to rest on an argument of the following nature : all valleys owe 

 their existence to the excavating power of rivers ; the submarine 

 troughs of the Antilles are valleys, and consequently were produced 

 by rivers. It was difficult to give unconditional assent to either of 

 these premisses ; although many valleys have undoubtedly beeu 



