ON THE GEOLOGICAL AGENCY OF THE WINDS. 225 



we should have a mean level between evaporation and precipita- 

 tion. If the former were in excess, the level of the Gulf waters 

 would sink down until the surface exposed to the air would be just 

 sufficient to return to the atmosj)here, as vapor, the amount of 

 water discharged by the rivers — the Mississippi and others, into 

 the Gulf. As the waters were lowered, the extent of evaporating 

 surface would grow less and less, until N'ature should establish 

 the proper ratio between the ability of the air to take up and the 

 capacity of the clouds to let down. Thus we might have a sea 

 whose level would be much farther below the water-level of the 

 ocean than is the Dead Sea. 



626. There is still another process, besides the two already al- 

 luded to, by which the drainage of these inland basins may, through 

 the agency of the winds, have been cut off from the great salt seas, 

 and that is by the elevation of continents from the bottom of the 

 sea in distant regions of the earth, and the substitution caused 

 thereby of dry land instead of water for the winds to blow upon. 



627. 'Now suppose that a continent should rise up in that part 

 of the ocean, wherever it may be, that supplies the clouds with the 

 vapor that makes the rain for the hydrographic basin of the great 

 American lakes. What would be the result ? Why, surely, few- 

 er clouds and less rain, which would involve a chancre of climate 

 in the lake country ; an increase of evaporation from it, because a 

 decrease of precipitation upon it ; and, consequently, a diminution 

 of cloudy screens to protect the waters of the lakes from being 

 sucked up by the rays of the sun ; and consequently, too, there 

 would follow a low stage for water-courses, and a lowering of the 

 lake-level would ensue. 



628. So far, I have instanced these cases only hypothetically ; 

 but, both in regard to the hydrographical basins of the ]\rexican 

 Gulf and American lakes, I have confined myself strictly to anal- 

 ogies. Mountain ranges have been upheaved across the course of 

 the winds, and continents have been raised from the bottom of the 

 sea ; and, no doubt, the influence of such upheavals has been felt 

 in remote regions by means of the winds, and the effects which a 

 greater or less amount of moisture brought by them would produce. 



629. In the case of the Salt Lake of Utah, we have an example 



