THE GEOLOGICAL AGENOx OF THE '\YINDS. 279 



the liycTrographic basin of tlie great American lakes. What would 

 be the result? Wtij, smely, fewer clouds and less rain, which 

 would involve a change 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 smi ; 

 and consequently, too, there would follow a low stage for water- 

 com'ses, and a lowering of the lake-level vfould ensue. 



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

 Examples. but, both ui regard to the hydrographical basms of 

 the Mexican Grulf and American lakes, I have confined myself 

 strictly to analogies. Mountain ranges have been upheaved across 

 the com'se of the ^inds, 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 moistm^e brought by them 

 woidd produce. In the case of the Salt Lake of Utah, we have 

 an example of drainage that has been cut off, and an illustration 

 of the j)roce3S by which Nature equalizes the evaporation and pre- 

 cipitation. To do this, in this instance, she is saltmg up the basin 

 which received the drainage of this inland water-shed. Here we 

 have the appearance, I am told, of an old channel by which the 

 water used to flow from this basin to the sea. Supposing there 

 was such a time and. such a vfater-com^se, the water returned 

 through it to the ocean v/as the amount by which the precij^ita- 

 tion used to exceed the evaporation over the whole extent of 

 country drained through this now dry bed of a river. The 

 winds have had something to do with this ; they are the agents 

 which used to bring more moisture from the sea to this water- 

 shed than they carried away ; and they are the agents which now 

 carry off from that valley more moistm^e than is brought to it, 

 and which, therefore, are making a salt-bed of places that used to 

 be covered by water. In like manner, there is evidence that the 

 great American lakes formerly had a drainage with the Gridf of 

 Mexico ; for boats or canoes' have been actually known, in former 

 years, and in times of freshets, to pass from the Mississippi Eiver 

 over into the lakes. At low water, the bed of a dry river can be 

 traced between them. . Now the Salt Lake of Utah is to the south- 

 ward and westward of our northern lake basin ; that is the quar- 

 ter (§ 357) whence the rain-winds have been supposed to come. 

 May not the same cause which lessened the precipitation or in- 



