PREVENTION OF EVAPORATION. G9 



through the valley, is checked by the trees, and when near the 

 surface of the earth, it probably does not move up the valley 

 •with half the rapidity it did. And then remember that, on the 

 surface, instead of passing over hot, barren sand, it passes over 

 fresh herbage, so that we have all through that valley a layer of 

 air that moves comparatively slow, and at the same time is 

 charged with moisture, so that, when it strikes the great Salt 

 Lake, instead of being a rapidly moving current of air, hot and 

 thirsty, it is moving comparatively slow, is nearly saturated 

 with water, and has no longer any ability to take up the waters 

 of the lake as it formerly did. Therefore the waters accu- 

 mulate, and so over the whole surface (and this is true of all 

 these places) evaporation is prevented by the introduction of 

 trees to prevent the rapid movement of the currents of air, and 

 also by covering the whole surface of the earth with this veg- 

 etation. That is my explanation of the increase of. water in 

 that valley. It is not that any more water has fallen there, — 

 perhaps not so much, certainly not any more, — but I believe it is 

 because the water is saved. 



But there is one thing that may seem to bear against this 

 theory. It is asserted by the Mormons — I cannot say whether 

 it is so or not — that the rains are more frequent in Salt Lake 

 City than they were twenty years ago, when they first came 

 there. That would seem to indicate that more water falls there. 

 Let us look at that a moment. I have been over this country, 

 back and forth, eight times, and have spent two seasons there, 

 and I have watched this thing very carefully. The rains they 

 speak of as falling in Salt Lake City and around there, are 

 showers ; and I have noticed this respecting them, that the 

 clouds are generally of small extent and hang very low. Every 

 shower that I have seen there has apparently commenced within 

 the mountain ranges. It appears as though these showers are 

 formed from the vapor rising from the valley, and condensed 

 by the cold currents of air that come over the mountains. As 

 there is a larger evaporating surface and less movement of wind 

 near the surface than formerly, more vapor accumulates in the 

 air than when the country was bare of vegetation. The water 

 that falls is not directly from the Atlantic or Pacific — in that 

 case it would be a real addition to the water in the valley — but 



