GEOLOGY. 267 



agency of the winds may with propriety consult, when he is told of an 

 inland basin, the water level of which, it is evident, was once higher 

 than it now is ; and that position is, that though the evidences of 

 a higher water level be unmistakable and conclusive, it does not follow, 

 therefore, that there has been a subsidence of the lake basin itself, or 

 an upheaval of the water-shed drained by it. 



Having, therefore, I hope, made clear the meaning of the question 

 proposed, by showing the manner in which winds may become impor- 

 tant geological agents, and having explained how the upheaving of a 

 mountain range in one part of the world may, through the winds, affect 

 climates, and produce geological phenomena in another, I return to 

 the Dead Sea, and the great inland basins of Asia, and ask : How far 

 is it possible for the elevation of the South American Continent, and the 

 upheaval of its mountains, to have had any effect upon the water level 

 of these seas ? There are indications that they all once had a higher 

 water level than they now have, and that formerly the amount of pre- 

 cipitation was greater than it now is. Then, what has become of the 

 sources of vapor ? 



A chain of evidence, which it would be difficult to set aside, can be 

 introduced, if required, to show that the vapor which supplies the extra- 

 tropical regions of the North with rains, comes in all probability from 

 the trade wind regions of the Southern Hemisphere. Now, if it be true 

 that the trade winds from, that part of the world take up there the 

 water which is to be rained in the extra- tropical North, the path as- 

 cribed to the S. E. trades of Africa and America, after they descend and 

 become the prevailing S. TV. winds of the northern hemisphere, should 

 pass over a region of less precipitation generally than they would do 

 if, while performing the office of S. E. trades, they had blown over 

 water instead of land. 



The S. E. trade winds, with their load of vapor, whether great or 

 small, take, after ascending in the equatorial calms, a north-easterly 

 direction. They continue to flow in the upper regions of the air, in 

 that direction, until they cross the Tropic of Cancer. The places of 

 least rain, then, between this tropic and the pole, should be precisely 

 those places which depend for their rains upon the vapor which the 

 winds that blow over S. E. trade wind of Africa and America convey. 



Now, if we can trace the path of these winds through the extra-trop- 

 ical regions of the northern hemisphere, we shall be able to identify 

 it by the foot-prints of the clouds ; for the paths of the winds which 

 depend for their moisture upon such sources of supply as the dry land 

 of Central South America and Africa, cannot lie through a country 

 that is watered well. 



It is a remarkable coincidence, at least, that the countries in the ex- 

 tra-tropical regions of the north, that are situated to the N. E. of the 

 S. E. trade winds of South Africa and America, that the countries 

 over which theory makes these winds to blow, include all the Great 

 Deserts of Asia, and the districts of least precipitation in Europe. Let 

 any one take a map of Mercators projection, and on it draw lines from 

 the Tropic of Cancer toward the north, to represent the probable^ route 

 and direction which the trade winds of the two southern continents 



