456 THE MOUNTAIN. 



Again, 



"The influence of mountains in extracting the water from the at- 

 mospheric currents which pass over them is well known and readily 

 explainable." 



Blodget, however, found that whatever might be the 

 source of our rains, when the water-carriers reached the 

 Alleghanies they were so far exhausted of their moisture 

 that those mountains extracted less from them than fell to 

 the westward, by some five or ten inches annually ; and that 

 the fall of rain upon them was less than upon the Atlantic 

 slope eastward of them to the ocean. This last announce- 

 ment does not accord with observations elsewhere made, but 

 is easily explained. 



As the storm approaches the ocean, it attracts in under it 

 the surface atmosphere of the ocean, loaded with vapor, con- 

 densing in the form of fog and scud as it becomes subject to 

 the increasing influence of the storm. Although the scud 

 or fog would not of itself make rain, it aids materially in 

 increasing the quantity of that which falls through it. " The 

 drops, by attraction and contact, enlarge themselves as they 

 pass through, in the same manner as a drop of water will do 

 in running down a pane of glass which is covered with mois- 

 ture. The small drop which starts from the upper portion 

 of a fifteen-inch pane will sometimes more than double its 

 size before it reaches the bottom." It is by this power of 

 attracting the surface atmosphere, which contains the mois- 

 ture of evaporation under it, and inducing condensation in 

 it, that the moisture of evaporation, which rarely rises very 

 far in the atmosphere, is made to fall again during storms 

 and showers. 



This attraction of a moist atmosphere from the ocean, 

 accounts for the excess of rain on the east of the Alle- 

 ghanies compared with its fall upon them. So the great 

 Yalley of the Mississippi is comparatively level, and less of 

 its water runs off than of that which falls upon the Allegha- 

 nies, and there is, therefore, more moisture of evaporation 

 in the atmosphere of the former to be thus precipitated and 



