EELATION OF LAKES TO CLIMATIC CONDITIONS. 83 



Aleng the margin of (xreat Salt lake, where the water is only a few 

 inches deej), it becomes so concentrated b}- evaporation that common salt 

 crystallizes and forms a brilliant white layer on the bottf)ni. In fording 

 an arm of the lake abont a mile broad, in order to reach Stan8l)ury island, 

 the writer, in 1880, found a crust of salt forming a glistening pavement 

 strong enough to support a horse and rider, but occasionally it would 

 give "vVay and lead to uncomfortable tlounderings in the black mud 

 beneath. 



The solubility of sodium sulphate is controlled largely by tempera- 

 ture. In Great Salt lake in summer it is all dissolved and the waters are 

 clear, but as cold weather a})proaches it separates and renders the waters 

 0[)alescent and somewhat milky in color. In the depth of winter, when 

 the tem[)erature falls below zero of the Fahrenheit scale, as it does at 

 times for days together, this salt separates in great abundance and is 

 thrown ashore by the waves in hundreds of tons, forming a slush-like 

 mass on the beach looking like soft snow. On such occasions it can be 

 gathered in practically unlimited quantities, but is soon re-dissolved when 

 the temperature rises. 



The brine of the lake is so concentrated that fish cannot live in it, but 

 it furnishes a congenial home for small crustaceans known as brine shrimps 

 (Artemia) and for the larvae of dipterous insects. These are abundant 

 at certain seasons, but not in such vast numbers -as in some of the more 

 alkaline lakes on the west side of the Great Basin. It has been stated 

 that the vast numbers of crustaceans and of larvae in these waters are due 

 to the fact that there are no fishes or other animals in the lakes that 

 could prey upon them ; aquatic birds, however, feed upon them in great 

 numbers, but still they swarm in countless myriads. Their food seems 

 to he minute algae of which several species have been described. 



As shown l)y the analysis given above, the principal salt in Great Salt 

 Lake is sodium chloride. In the second exanqjle of the saline lakes 

 descriljcd below the characteristic ingredients are sodium carbonate ami 

 s(»(hiuii sulphate. (Jreat Salt lake may be said to be a salt lake in 

 distinction fiom a number of water bodies situated especially on the 

 west side ()[' I lie Great Basin, which may with propriety be designated 

 as alkaline lakes. 



Mono lak<', (aliloriiia. — This lake, selected as the type of a series 

 of strongly alkaline water-bodies in tlie deseit Itasiiis of the Arid region, 

 is situated in soutii-easteni ( 'alifornia, within a irw niih's of the Neva<la 



