356 BASIN OF THE GULP OF MEXICO. 





the Red River of Nachitoches, so that the northern part only 

 of the state of Illinois is covered with gramma. This line 

 of demarcation is not only interesting for the geography 

 of plants, but exerts, as we have said above, great influence 

 in retarding culture and population north-west of the Lower 

 Mississippi. In the United States, the prairie countries 

 are more slowly colonized ; and even the tribes of independent 

 Indians are forced by the rigour of the climate to pass the 

 winter on the banks of rivers, where poplars and willows 

 are found. The basins of the Mississippi, of the lakes of 

 Canada and the St. Lawrence, are the largest in America ; 

 and though the total population does not rise at present 

 beyond three millions, it may be considered as that in 

 wliich, between latitude 29 and 45 (long. 74 94), civili- 

 zation has made the greatest progress. It may even be said 

 that in the other basins (of the Orinoco, the Amazon, and 

 Buenos Ayres), agricultural life scarcely exists ; it begins, on 

 a small number of points only, to supersede pastoral life, and 

 that of fishing and hunting nations. The plains between the 

 Alleghanies and the Andes of Upper Louisiana are of such 

 vast extent, that like the Pampas of Choco and Buenos 

 Ayres, bamboos (Ludolfia miega) and palm-trees grow at one 

 extremity, while the other, during a great part of the year, 

 is covered with ice and snow. 



II. TlIE BASIN OF THE GrTJLF OF MEXICO, AND OF THE 



CARIBBEAN SEA. This is a continuation of the basin of the 

 Mississippi, Louisiana, and Hudson's Bay. It may be said, 

 that all the low lands on the coast of Venezuela situated 

 north of the littoral chain, and of the Sierra Nevada de 

 Merida, belong to the submerged part of this basin. If I 

 treat here separately of the basin of the Caribbean Sea, it is 

 to avoid confounding what, in the present state of the globe, 

 is partly above and partly below the ocean. The recent 

 coincidence of the periods of earthquakes observed at Caracas, 

 and on the banks of the Mississippi, the Arkansas, and the 

 Ohio, justifies the geologic theories which regard as one 

 basin the plains bounded on the south, by the littoral Cor- 

 dillera of Venezuela; on the east, by the Alleghanies and 

 the series of the vo-lcanos of the "West Indies ; and on the 

 west, by the Itocky Mountains (Mexican Andes) and by the 



