88 GEOLOGY. 



importance, and may be briefly alluded to bere. It was formerly supposed tbat no natural 

 reservoirs of fresb water sufficient for the supply of men and animals existed over the entire 

 distance of 80 miles, from the mountain base to the Colorado river. The subsequent discovery 

 of extensive depressed areas, as that constituting "New River," retentive both of rain water 

 and river overflows, has materially shortened these "dry stretches," as they are termed, 

 especially in certain seasons. Due to the same general cause, depressed areas, that have no 

 connexion with flowing water, are the salt lakes of greater or less extent ; the degree of saline 

 impregnation necessarily varying according to the amount of aqueous supplies from local rains. 

 The water, however, is rarely, if ever, suitable for drinking purposes. 



Even on the higher upland plateaus water is occasionally found in the beds of shallow 

 streams, where the product of recent rains is retained by a clay substratum, the upper sandy 

 layers serving to check the evaporation ; but such uncertain sources cannot, of course, be safely 

 depended on during the greater part of the year. 



The practical question arises, whether permanent water can be obtained by piercing the 

 coarse sandy layers to a sufficient depth to reach a still lower impervious stratum ? As bearing 

 on this question we may cite the irregular character of the argillaceous beds, as seen in various 

 exposures of the lower strata. This irregularity of strata indicates the great probability of 

 finding lower basins of water of considerable extent and capacity connected with sources of 

 supply sufficiently elevated to flow over the surface at the point of excavation. 



Still another important question would come up, whether the water reached by permeating 

 throuo-b such a depth of saline soil would not be so much impregnated with saline matters as 

 to be unfit for use ? But these are questions to be determined by direct experiment, and not by 

 theory. 



The "New Eiver" formation, in a geological point of view, must, as we have before re- 

 marked, be regarded only as a natural depression in the tertiary series, having a direct con- 

 nexion with the fiowing water of the Colorado river. Its original lacustrine character is 

 sufficiently seen and limited by the presence of fossil fresh water shells, including species 

 identical with those now found living in lagoons adjoining the Colorado. Among these we 

 notice Planorhis, Pliysa, Anandorita ; and besides these a small univalve near Ressoa, quite 

 abundantly scattered, and often drifting in small heaps over the alluvial sandy tracts which 

 adjoin the lower depressions. 



The further relation of these facts to vegetation and agricultural capacity will be alluded to 

 elsewhere. 



MINERAL PRODUCTIONS OF SOUTHERN CALIFORNIA. 



• 



The inferences to be drawn from the above geological sketch, as regards the actual or pros- 

 pective mineral products of this region, may here be properly summed up, following out the 

 same general order as before laid down. 



1st. The preponderance of the crystalline granite rock«, constituting, as we have seen, the 

 great body of this mountain range, is unfavorable to the existence of extensive or valuable 

 mineral products. Neither does this view seem at present likely to prove erroneous by the 

 recent impulse given to mineral discoveries on this coast. 



Many persons, arguing solely from the general similarity of features between certain sections 



