IRRIGABLE LANDS OF THE SALT LAKE DRAINAGE SYSTEM. 127 
Nineteen tracts have not yet been surveyed by the land office. 
The total area of the district is 13,370 square miles, of which one- 
tenth of one per cent. is cultivated, and one-fourth of one per cent. may be 
cultivated. 
The contrast between the districts east and west of Great Salt Lake 
illustrates the combination of physical conditions essential to agriculture in 
our arid territories. An atmosphere endowed with but a small share of 
moisture precipitates freely only when it is reduced to a low temperature. 
Agriculture is dependent on the precipitation of moisture, but cannot endure 
the associated cold climate. It can flourish only where mountain masses 
turn over the aqueous product of their cold climates to low valleys endowed 
with genial climates. The Wasatch and Uinta crests stand from 6,000 to 
9,000 feet higher than the valleys bordermg Great Salt Lake. Their 
climate has a temperature from 20° to 30° lower. The snows that accu- 
mulate upon them in winter are not melted by the first warmth of spring, 
but yield slowly to the advancing sun, and all through the season of 
erowing crops feed the streams that water the valleys. The Bear, the 
Weber, and the Jordan carry the moisture of the mountains to the warmth 
of the valleys, and fertility is the result. 
To the north and west of the lake there are many mountains, but 
they are too low and small to store up snow banks until the time of need. 
Their streams are spent before the summer comes; and only a few springs 
are perennial. The result is a general desert, dotted by a few oases. 
