the immediate cause of the desc 

 affecting more equally the whole 

 present time. 



The quantity of evaporate* 

 shallowest places become dry, an 

 but the quantity of condensed m 

 decrease proportionally. The ah 

 actually decreasing proportional 

 the shore-lines become more an 

 will be reduced or discontinue 

 barren and depopulated. Thus t 



In the southern, less elevate, 

 is even more unfavorable. The < 

 nominal. 



ng the si 



of moisture. Rivulets and creeks run down in every direction. Many of these sink 

 in the absorbent sand of the valleys as soon as they reach the foot of the mountains. 

 Others continue on even to more distant points, until they sink or join larger water- 

 courses. 



The water absorbed at one point frequently returns to the surface at a lower place, 

 forced up by an impervious stratum of clay or by a rocky barrier, especially where 

 a valley is contracted by projecting spurs of bills or a branch valley unites with the 

 main valley. Often the water sinks again immediately after the barrier has been 

 crossed, within a few yards of its rise. At other points the water regains the surface 

 because the sand is saturated to its lull extent. Thus secondary springs are formed, 

 frequently in the shape of ponds. 



or overflown at numerous points. During the other seasons die affluence is smaller, 

 many creeks and springs discontinue, and the subterranean reservoirs, termed of the 

 sand at the bottom of the valley which has been saturated in the spring, are emptied 

 by evaporation, and by supplying the springs and creeks with which they connect. 



The creeks and rivers form either lakes, the water of which disappears by evapo- 

 ration, and the surplus of it is absorbed in the wet season by the adjoining sand-flats, 

 or they dry up gradually and sink in the thirsty sand without even forming lakes. 



The aridity of the climate and consequent amount of evaporation may be judged 

 from the fact that during our survey the difference between the dry and the wet bulb 

 thermometer frequently indicated a nearly complete absence of moisture in the atmos- 

 phere. This was observed even on the shores of Carson Lake and in Carson Valley, 



