58 On the Laws ivkich regulate the 



Rio Bravo del Norte, rises about lat. 38° N., flows into Gulf of Mexico. 

 Orinoco, rises in lat. 2° to 10° N., flows into North Atlantic. 

 Amazon, rises in Peruvian Andes and Parime mountains, from lat. 4° N. to lat 

 20° S., flows into Atlantic at the equator. 



TOCANTINS, v 



Paranahyba, I rise in Brazilian mountains, flow into South Atlantic. 



San Francisco,/ 



La Plata, rises in Chilian Andes and north-east mountains of Brazil, lat. 13° 



to 15° S. 



Mendoza, \ .„..,. 



w „ rur~„ t „„« f rise in Chilian Andes, flow into South Atlantic. 



Negro or Cusu Lebu, J 



From this table it will be apparent that the great rivers of 

 Central Asia, the Ganges, the Brahmapootra, the Hoang-Ho, 

 have their origins about the parallel of thirty-one north ; 

 while the large rivers of Northern Asia, the Obi, Yenesei 

 and Lena have their sources about the forty-eight and fiftieth 

 degrees of latitude. The great rivers of South America — 

 the Amazon, the Orinoco, and La Plata — rise within the tro- 

 pics ; and there is no river of any consequence in the south- 

 ern hemisphere which derives its origin beyond latitude 40° 

 south. 



In North America, the Mississippi rises in latitude 47°, the 

 Missouri in 42° north, while their numerous tributaries have 

 their origin and courses in much lower latitudes. This is the 

 case, too, with the principal rivers of Europe. The extreme 

 northerly sources of the Volga, Ural, Don, and Dnieper, lie 

 between the parallels of fifty-seven and fifty-four ; but they 

 are fed chiefly by tributaries which traverse the parallels of 

 forty and forty-five degrees. The Danube, the Rhone, and 

 the Rhine, have their origins in lat. 46° to 47° north. 



The primary cause of this arrangement of river sources 

 seems to be very obvious, and evidently has a relation to the 

 regions of the greatest and most constant deposition of mois- 

 ture on the earth's surface. Thus the greatest amount of 

 annual precipitation occurs within the tropical and sub-tro- 

 pical regions, while the fall of rain decreases in a rapid ratio 

 towards the frigid zones. While 100 to 300 inches of rain 

 fall annually in the tropics, from 30 to 25 inches is the 

 average of the temperate zones, and from 16 to 10 inches of 

 the sub-frigid and frigid zones. 



