FEESHENING OF LAKES BY DESICCATION. 



225 



As these lake basins were never filled to overflowing, we are forced to 

 conclude that influx was counterbalanced solely by evaporation, and that 

 dui'ing periods of extreme desiccation the saline deposits became buried 

 and absorbed by the marls and clays which accumulated in the valleys. 



Having analyses of the waters of an inclosed lake, and knowing also 

 the composition of its tributaries, we can determine, at least approximately, 

 the length of time it has been in existence, provided no salts pi'eviously 

 deposited were dissolved when the basin commenced to fill. For the 

 purpose of making a computation of this nature in the case of the lakes 

 now occurring in the Lahontan basin, the following table has been com- 

 piled from analyses given in chapter 111. 



Table D. — Composition of the princijial lakes and rivers of the Lahontan basin. 



LAKBS. 



In 1,000 parts of water. 



Pyramid 

 (average of 

 4 analyses). 



Silica (SiOs) 



Calcium (Ca) 



ilagnesium (Mg) 



Potassiunj (K) 



Sodium (Na) 



Sulphuric acid {SO4) 



Chlorine (CD 



Carbonic acid (CO3) by differ- 

 ence 



Total 



0.0334 

 0. 0089 

 0. 0797 

 0. 0733 

 1. 1796 

 0. 1822 

 1.4300 



0. 4990 



3. 4861 



Walker 

 (average of 

 2 analyses). 



0. 0075 

 0. 02215 

 0. 0383 

 trace 

 0. 85535 

 0. 5200 

 0. 58375 



0. 47445 



Winnemncca, 



0. 0275 

 0. 0196 

 0. 0173 



0. 0686 



1. 2070 

 0. 1333 

 1.6934 



0. 3458 



Average. 



0. 02280 

 0. 01688 

 0. 0451 



0. 04730 

 1. 11065 

 0.2785 



1. 23'IS8 



Probable combination in average compo- 

 sition. 



2.60150 I 



I 



Silica (SiOi) 



Calcium carbonate (CaCOs) . 

 Magnesium carbonate (Mg 



CO3) 



Sodium carbonate (NaCOs) - . 

 Potassium chloride (KCl) ... 



Sodium t hloride (NaCI) 



Sodium sulphate (Na2S04) . . 



Total (99.U0 percent. ac- 

 counted for) 



0. 02517 

 0. 03221 



0. 20483 

 0. 48327 



0. 09894 



1. 94244 

 0. 40195 



3.18881 



KIVERS. 



MoN. XI 15 



