Proceedings of the PoLYTEcnmc Association. 983 



this decomposed material to be washed do\rii into lower lands. By 

 these means the lower lands are gradually elevated. As the valleys 

 through which rivers run narrows upon them, their currents increase 

 in swiftness, and more material is carried into the sea and deep 

 water, and deposition takes place along shore lines. 



Hence you see, that on the map of thedilurial, the growUi of the 

 continent lias been along the great inland waters, and the ocean con- 

 tiguous to the mouth of great rivers. From Cape St. Rogue to the 

 Amazon tlie coast line has been modified by the constant setting in 

 of currents from the Atlantic carried by the trade winds. From the 

 mouth of the Amazon on to the island, of Trinidad the wash of this 

 river and the Oronoco have contributed to build the shore line out 

 seaward. The same remark applies to all other streams. The wash 

 'of the Andes has enlarged by a very narrow strip the coast line of 

 the Pacific. 



From this rapid survey of the great changes of the continent during 

 the diluvial period, I think we can learn the agencies that contributed 

 to build this continent in geological ages, such long time past no 

 liorologue can measure. 



They are briefly these : 



First. Molecular decomposition of rock masses by chemical, atmos- 

 pheric and other agencies, sub-aerial changes. 



Second. Removal and transportation of this decomposed material 

 by the agency of flowing water ; and 



Third. Redeposition of this material by change of velocity of trans- 

 porting currents, and to dull action. 



There remain for discussion the dynamics, which have thrust down 

 large continental areas to receive depositions from the sea, and, re-ele- 

 vated them to become again dr^^ land. 



May we expect that henceforth the growth of the continent shall 

 be seaward, and that the streams flowing outward, from south and 

 north American continents, aided by detritus of the West Indian 

 Islands, shall fill up the Caribbean sea and all the channels between 

 the island, the Gulf of Mexico, and, finally, the two continents become 

 one, not by the present narrow belt, but a new, noble, large and 

 rounded out-growth? These are questions for the coming geologists. 



Adjourned. 



