58 



GEOLOGICAL HISTOKY OF LAKE LAUONTAN. 



Water of Pyramid LaJce collected in Auyusty 1882, at a, north of Anaho Island {see Plate IX). 



Constituents. 



SiHcatSiOa) 



Magnesium (Mg) 



Calcium (Ca) 



Sodium (Na) 



Potassium (K) 



Chlorine (CI) 



Snl]iliuric acid (SO4) 



Ciirbouic acid (CO3) by difference 



Total ! 3 4987 



Constitnents. 



Pidbalile com- 

 bination (ex- 

 prt'ssed in 

 grammes per 

 liter). 





'3.+- » 



! ag:i 



Silica (SiOj) I 0. 



Magnesium carbonate (MgCOg). . . 0. 



Calciuai carbonate (CaCOa) 0. 



Polaasiiim chloride (KCl) 0. 



Sodium cbloridc (NaCl) ,2. 



Sodium sulphate (NaaSOa) 0, 



Sodium carbonate (NaaCOa) 0, 



Total* 



041'; 



2800 

 0447 

 1474 

 2411 

 2607 

 4738 



a ® H 

 to 



0. 0200 

 0. 2818 

 0.0447 

 0. 1381 

 2. 2550 

 0. 2737 

 0. 4756 



* 99.94 per cent, accounted for in : ample from 1 foot below surface, and 100. 15 per cent, (error 0. 15 per cent.) in the 

 remaining sample. 



All the water samples from Pyramid Lake when analyzed contained a 

 small quantity of suspended flakes of calcareous and siliceous matter, which 

 had separated since the samples were bottled. 



These analyses show much less difference in the composition of the water 

 near the northern and near the southern ends of the lake than was antici- 

 pated ; and the examination of top and bottom samples fails to indicate an 

 increase in salinity with increase in depth, such as was found by Lartet in 

 the case of the Dead Sea."" The bearing of the present composition of Pyr- 

 amid Lake on the interpretation of the history of the ancient lake which 

 flooded the same basin will be considered in connection with the chemistry 

 of the other lakes of the basin. Standing alone, the analyses of the water 

 of the present lake are of geological interest as showing the composition of 

 wiiters that ai-e now depositing calcareous tufa of the same general character 

 as that first found in Lake Lahontan. 



During our measurements of the depth of the lake the cup at the end 

 of our sounding lead seldom failed to bring up a specimen of the bottom. 

 From the samples llms obtained we learn that the bottom near shore is usu- 



'" Exploration G(5ologique fie l.a Mer Morte, Paris, 1877, p. 278. 



