266 ANNUAL OF SCIENTIFIC DISCOVERY. 



of the ocean, I again ask, comes the vapor which forms the rains that 

 fall on that immense water-shed to which the lakes give drainage ? 

 My investigations have suggested the idea that they come from the 

 trade- wind region of the South Pacific Ocean. Now suppose that a 

 continent should rise up in that part of the ocean, wherever it maybe, 

 that supplies the clouds with the vapor that makes the rain for the lake 

 water-shed what would be the result? Why, surely, a change of 

 climate in the lake country. An increase of evaporation, because a 

 decrease of precipitation ; 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. 



In the case of Utah, we have an example of drainage that has been 

 cut off, and an illustration of the process by which Nature equalizes 

 the evaporation and precipitation. 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 waters 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 precipitation 

 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, 

 probably, to do with this. They are the agents which vised to bring more 

 moisture to this water-shed than they took away ; and they are the agents 

 which now carry off from that valley more moisture than is brought to 

 it, and which, therefore, are here 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. 

 Steamers have been actually known, in former years and in times of 

 freshets, to pass from the Mississippi over into the lakes. At low 

 water, the dry bed of a river can be traced between them. Now the 

 Salt Lake of Utah is to the southward and westward of our northern 

 lake basin. That is the quarter whence the rain winds have been sup- 

 posed to come. May not the same cause which lessened the precipi- 

 tation, or increased the evaporation in the Salt Lake water-shed, have 

 done the same for the water-shed of the great American system of 

 lakes'? If the mountains to the west, the Sierra Nevada, stand higher 

 now than they formerly did, and if the winds which fed the Salt Lake 

 valley with precipitation had, as I suppose they have, to pass the sum- 

 mits of these mountains, it is easy to perceive why the winds should 

 not convey as much vapor across them now as they did when the summit 

 of the range was lower and not so cool. The Andes, in the trade wind 

 region of South America, stand up so high that the wind, in order to 

 cross them, has to part with all its moisture, and, consequently, there 

 is on the other side a rainless region. Now, suppose a range of such 

 mountains as these to be elevated across the track of the winds, which 

 supply the lake country with rain, it is easy to perceive how the whole 

 country, watered by the vapor which such winds bring, would be con- 

 verted into a rainless region. I have used these hypothetical cases to 

 illustrate a position which any philosopher who considers the geological 



