136 BOARD OF AGRICULTURE. 



excessive falls of rain take place only at certaiti elevations. In 

 India, that elevation is 4500 feet. The rain clouds pass up to that 

 altitude before the chill of condensation takes place, which secures 

 the greatest amount of precipitation. When the clouds pass to a ■ 

 higher elevation, since they have been robbed of their moisture, 

 the amount of rain that falls from a greater altitude is less than 

 the amount at about that height. In India, as I have said, 4500 

 feet is the altitude of greatest precipitation. In England, it is 

 only 1900 feet, and at that height in the atmosphere the largest 

 amount of precipitation takes place. 



The fourth modif3'ing circumstance is proximity to mountains. 

 Rainfall is iijfluenced by proximity to mountains ; not so much 

 from the chill of elevation, not so much from the direct efiect of 

 mountains as condensers, as from these causes together with the 

 movements of the air which the mountains themselves beget, by 

 which their influence is extended beyond their base. At Vera 

 Cruz, on the eastern coast of Mexico, just west of the Gulf, there is 

 an annual rainfall of one hundred and eighty inches, which is 

 about twice tke mean quantity for the Gulf of Mexico. The cause 

 of this is traced to the range of mountains just west of the city. 

 The influence of the mountain is extended beyond its base to a 

 distance of several miles around. The quantity of rainfall is 

 greater moreover upon the windward than upon the leeward side 

 of mountains. In the Scandinavian peninsula, at Bergen, Nor- 

 way, the annual rainfall is 82 inches. Just over the other side of 

 the peninsula, at Stockholm, it is 21 inches. The western coast of 

 Norway, the windward side, is exposed to the prevailing south- 

 west wind, and hence the much larger rainfall than that on the 

 leeward side. We have an admirable illustration of this principle 

 in South America, where is found the grandest river system in the 

 world ; the Amazon carrying down to the ocean, a burden of 

 water more than three times as great as that conveyed by any 

 other known river. We have here in this river system not only 

 the Amazon, but the La Plata and the Orinoco, noble rivers sup- 

 plied by the abundant rains on the eastern slopes of the Andes. 

 Here the principal rainfall takes place on the eastern side of the 

 mountains, very large quantities of rain falling on that side, while 

 the amount on the western side is very small indeed ; so small, 

 that along the western coast of Peru, for the distance of 700 miles, 

 the region is entirely destitute of rain, not a drop falling once in a 

 century. 



