December 17, 19 14] 



NATURE 



435 



which has been the scene of alternate submergence 

 and desiccation. 



The Cahuilla basin, lying to the west of the lower 

 (southern) portion of the main delta of the Colorado 

 River, was in Tertiar\- times cut off from the sea and 

 so became a brackish inland lake (Lake Cahuilla). 

 The lake bed, now called the Salton Sink, has its 

 upper margin about 20 ft. above mean tide-level, while 

 its lowest point, now beneath the water of the present 

 lake (Salton Sea), is 280 ft. below this level. On 

 either hand of the Sink, which is oblong in outline 

 (about eighty miles long and thirty- miles in greatest 

 width), there rise arid and sun-scorched low moun- 

 tains, chiefly of granite, the slopes and waterless 

 canons of which bear a scanty vegetation. The Sink 

 is practically a level plain, with no irregularities of 

 surface to varj- the effects of sun and wind, with a 

 uniform temperature and uniform deficiency of atmo- 



A rocky island in the SaUon Sea, Southern CaKfomia, formerly >uuuicrgc(. but :iow ejiptocti oy mr: icucimou oi' ihe lake owing 

 to continoed evaporation. The rock shows colonisation by a desert shrub, Pluchea sericea (Compositz). 



spheric humiditv and precipitation, the latter being 

 on the average 2-7 in. a year. The ancient lake which 

 originally filled the Sink had almost or entirely dis- 

 appeared by evaporation, leaving a series of beach- 

 lines, but during 1905 and 1906 the cutting of canals 

 and the resulting escape from control of the Colorado 

 River water resulted in a partial re-flooding of the 

 basin and the formation of the Salton Sea, threaten- 

 ing the restoration of the former lake conditions and 

 necessitating the removal of the Southern Pacific Rail- 

 way track for sixtA'-seven miles to a higher bed. In 

 I907. however, the railway engineers stopped the 

 deluge by re-diverting the Colorado water to the Gulf 

 of California, and the gradual disappearance by 

 evaporation of the Sea then began and is still in pro- 

 gress. Since 1907 the average annual rate of lower- 

 ing of level by evaporation has been about 5 ft., while 

 the concentration of the water has risen until the 



NO. 2355, VOL. 94] 



proportion of total solids is now more than i per cent. 

 Succeeding the chapters on the geology, geography, 

 climate, and water analyses, the remainder of the 

 report (pp. 48-182) is devoted to the biological results 

 obtained. Prof. G. J. Peirce gives an interesting 

 account of the behaviour of the micro-organisms found 

 in the Salton Sea, and in the strong brines from 

 which salt is crj'stallising out naturally or in the 

 artificial salt-pans on the shores of the lake. It has 

 long been known that various organisms live under 

 what are commonly regarded as fatal conditions — e.g. 

 the mould-fungi which thrive on solutions of strj'ch- 

 nine, formalin, carbolic acid, etc., the insects in oil- 

 wells and asphaltum, those in hot springs and in 

 snow, and so on — but in these cases the conditions are 

 fairh' stable, and it is harder to understand how 

 organisms like the brine-shrimps (Artemia) and 

 various protozoa, flagellates, and algae found in the 



Salton Sea and 

 other strong brines 

 can exist under 

 conditions ranging 

 from rain-diluted 

 sea-water to con- 

 centrated brine 

 from which com- 

 mon salt crystal- 

 lises. The lower 

 organisms u po n 

 which the brine- 

 shrimps and proto- 

 zoa feed are mainly 

 Pyramimonas, 

 Dunaliella, C a r- 

 teria, and various 

 bacteria. The latter 

 are entirely different 

 from the bacteria 

 which cause putre- 

 faction in waters 

 of the usual con- 

 centrations, and 

 which are killed by 

 the Salton brine — 

 a concentrated solu- 

 t i o n of sodium 

 chloride and of 

 magnesium salts. 

 The most conspicu- 

 ous are a chromo- 

 genic form which 

 gives a red colour 

 to the salt in the 

 salt-pans and to 

 fish pickled in the 

 salt, and a cellu- 

 lose - destroying 

 form which attacks stems and other plant-remains 

 submerged in the lake. 



The present flora of the Salton Sink includes 179 

 species of seed-plants, the great majority being salt- 

 plants (halophytes) and plants adapted for life under 

 dr}- conditions (xerophytes) ; the former are mainly 

 members of the Chenopodiaceae. Apart from the salt- 

 mud plants, the vegetation of the Sink is a part of the 

 general flora of the Colorado desert, differentiated 

 mainly by the great preponderance of species of the 

 orache genus (Atriplex) in its composition, and it is 

 of a remarkably uniform character. Three plain com- 

 munities or associations can be distinguished, accord- 

 ing to the nature of the soils — coarse-grained, detrital 

 slopes, clays, and mound-forming drifted materials. 



The longest report (pp. 115-72) is that by Dr. Mac- 

 Dougal, dealing with the movements of vegetation 

 in the area. The phenomena observed on the emersed 



