290 THE PHYSICAL GEOGRAPHY OF THE SEA. 



the hydrographic basin of the great American lakes. What 

 would be the result? Why, surely, 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 pro- 

 tect 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. 

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

 Examples. but, both in regard to the hydrographical basins of 

 the Mexican Gulf and American lakes, I have confined myself 

 strictly to analogies. 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 ef- 

 fects which a greater or less amount of moisture brought by them 

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

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

 of the process by which Nature equalizes the evaporation and pre- 

 cipitation. To do this, in this instance, she is salting 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 water-course, the water returned 

 through it to the ocean was the amount by which the precipita- 

 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 moisture 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 Gulf 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- 



