[NTRODUCHON 17 



The lowland strip on the Pacific side of our area is a 

 narrow fringe. Like the central plateau it is for the 

 most part arid, but irrigation makes it productive. The 



lowlands of the Atlantic side are generally wet and 

 heavily forested. The greatest land mas- of uniformly 

 low elevation is the Peninsula of Yucatan. In eastern 

 Honduras and Nicaragua there are extensive river 

 valleys of low elevation. 



The river systems of Mexico and Central America 

 How into the two bounding oceans or into lakes which 

 have no outlets. Several closed basins occur on the 

 Mexican table-land. The Rio Nazas and the Rio 

 Xieves flow into salt marshes in the northern state of 

 Coahuila. But the most important interior basin is 

 the Valley of Mexico. In this mountain enclosed val- 

 ley, whose general level is 7,500 feet above 4 the sea, there 

 are five lakes which in order from north to south are 

 named Tzompanco, Xaltocan, Tezcoco, Xochimilco, 

 and Chalco. The last two contain fresh water, since 

 they drain into Lake Tezcoco, but the rest are more or 

 less brackish. Lake Tezcoco i- by far the larg 

 although its area has been greatly reduced by natural 

 and artificial causes since the coming of the Spaniards. 



The largest river of Mexico is the Rio Lerma which 

 takes the name Rio de Santiago during its deep and 

 tortuous passage from Lake Chapala to the Pacific. 

 Farther to the south is the Rio de la- Balsas which like- 

 wise flow- into the western ocean. The name means 

 "River of the Rafts" and i- given because of a peculiar 

 floating apparatus made of gourds tied to a wooden 

 framework that i- used on this stream. Mowing into 

 the Gulf of Mexico are several Large streams, among 

 which may be mentioned the Panuco, Alvarado, 

 ( rrijalva, and Usumacinta. The last is by far the gn at- 

 est in volume of water, and with it- maze of tributaries 



