602 SOIL BELOW EOCK. 



In an able and interesting article in a California magazine, Dr. 

 "Widney has suggested a probable cause and a possible remedy for 

 the desiccation of Southeastern California referred to in a former 

 chapter. The Colorado Desert, which lies considerably below the 

 level of the waters of the Gulf of CaHfornia, and has an area of 

 about 4,000 square miles, evidently once formed a part of that 

 gulf. This northern extension of the gulf appears to have been 

 cut off from the main body by deposits brought down by the 

 great river Colorado, at no very distant period. These deposits 

 at the same time turned the course of the river to the south, and 

 it now enters the guK at a point twenty miles distant from its 

 original outlet. 



When this northern arm of the gulf was cut off from the sea, 

 and the river which once discharged itself into it was diverted, 

 it was speedily laid dry by evaporation, and now yields no vapor 

 to be condensed into fog, rain and snow on the neighboring moun- 

 tains, which are now parched and almost bare of vegetation. 



The ancient bed of the river may still be traced, and in floods 

 the Colorado still sends a part of its overflowing supply into its 

 old channel, and for a time waters a portion of the desert. It is 

 behoved that the river might easily be turned back into its orig- 

 inal course, and indeed nature herself seems to be now tending, 

 by various spontaneous processes, to accomplish that object. The 

 waters of the Colorado, though perhaps not suflBcient to fill the 

 basin and keep it at the sea-level in spite of the rapid evaporation 

 in that chmate,* would at least create a permanent lake in the 

 lower part of the depression, the evaporation from which. Dr. 

 Widney suggests, might sensibly increase the humidity and lower 

 the temperature of an extensive region which is now an arid and 

 desolate wilderness. 



Soil ielow Rock. 



One of the most singular changes of natural surface effected 

 by man is that observed by Beechey and by Barth at Lin, Tefla, 

 and near Gebel Genunes, in the district of Ben Gdsi, in North- 

 em Africa. In this region the superficial stratum originally con 



* The thermometer sometimes rises to 120° F. at Fort Tuma, at the S.E. 

 angle of California in N. L. 38°. 



