in the same latitude on the western side of the same monntains it never rains, and 

 ve<retation can only be promoted by irrigation. 



The researches of Herndon and Gibbons, in their exploration of the Amazon 

 River of South America, fully explain this phenomenon. The tropical current of 

 air, flowing as it does along the equator, from east to west, carries with it from off 

 the Atlantic large quantities of moisture ; this is gradually distributed across the 

 continent, until reaching the barrier of the Andes Mountains, where the accumu- 

 lated vapors are precipitated in heavy rains, while the air, in passing over those 

 snow clad summits, has every particle of moisture congealed, and precipitated in 

 snow ; so that when the air reaches the western side it is entirely deprived of 

 moisture, consequently there can be no rain there. In some parts of the earth, 

 the wiuds blow in one direction for six months of the year, and in other directions 

 for the other six months. Along the equator the current of air is from east to 

 west, while in the northern temperate zone, the general current is more from west 

 to east. Here, however, there are modifying influences, such as ocean currents, 

 mountain ranges, inland lakes, &c., that prevent any uniform currents of wind; 

 hence we see that variableness in the direction of the current of air so valuable in 

 the temperate regions, making far less deserts in them than where the currents of 

 air are more uniformly in one direction. 



It is more than probable that the extremes of heat and cold would be greater 

 in a country deprived of its timber, but it by no means follows that the rains 

 would be less frequent. Dews are heavier in cultivated valleys than in those 

 covered with wood, and there is reason to believe that a larger portion of the rain 

 penetrates the soil in a cultivated field than it would do if in forest. It has often 

 been observed that springs augment in volume as the land around becomes more 

 cleared of its timber. 



There is doubtless much yet to learn as to the reasons why some portions of 

 the earth's surface are productive, and others are barren ; but it is hardly consist- 

 ent with what we do know, to assert that to deprive the interior of a continent of 

 its timber would render it "a dry desert." It never could have been anything 

 but a " dry desert" if such would be the effect. 



-f2^ 



