Z THE SALTON SEA. 



The discovery of this practicable and easy railway route determined the construc- 

 tion of a southern railroad and made it necessary to acquire from Mexico the strip of 

 country in southern Arizona since known as the "Gadsden Purchase." 



We descended with eagerness into this great unknown valley, carefully reading the 

 barometer at regular distances to ascertain the grade. Proceeding without obstacles, but 

 with no trace of a road, and following the dry bed of a stream, now known as the White- 

 water, we reached the bed of a former lake and found it to be below the level of the sea. 

 (Plate 1 c.) 



The value of this pass, as a great natural gateway through the mountains from the 

 ocean to the interior, is emphasized by the magnificence of the mountain masses rising 

 like sentinels, on the north and on the south. These are San Bernardino, over 11,000 feet 

 anil snow-capped for the greater part of the year ; and San Jacinto, the sharp peak on the 

 south with rugged sides, and similar elevation, which forms the northern end of the Penin- 

 sula Range. 



This San Gorgonio Pass is the only great break directly through the mountains from 

 Cape St. Lucas to the Golden Gate; and like the Golden Gate, it is a great draft channel 

 for the inrush of ocean winds to supply the uprising heated air of the interior deserts. 

 Topographically this valley into which we descended is the northwestern extension, pro- 

 longation, or head of the Gulf of California. 



GEOLOGIC HISTORY. 



That this valley was formerly occupied by sea-water is shown by the reefs of fossil 

 oysters and other marine shells. As these fossils are now above tide-level, it is evident 

 that there has been a considerable uplift of the whole region, and a change from marine 

 to fresh-water conditions. Further north on the west coast of the United States we have 

 another great longitudinal valley separating the Coast Range of California from the 

 Sierra Nevadas. The two great valleys are similar in many respects; they both receive 

 the drainage of the larger rivers of the interior and protect the deltas of their rivers from 

 the direct destructive or modifying action of the sea. In the Gulf of California we find 

 the Delta of the Colorado, and in the California valleys the deltas of the San Joaquin 

 and of the Sacramento Rivers. The California Valley is nearly at the sea-level. The sea 

 has been displaced by alluvium. A depression of the western coast of less than 1,000 feet 

 would flood the valley with sea-water through the Golden Gate from the Tejon to Shasta. 

 A similar or even less depression of the Lower California region would carry the waters 

 of the Gulf far north of Yuma and flood the valleys for 200 miles northwest of the present 

 head of the Gulf. A depression of 2,580 feet would connect the water of the Pacific and 

 the Gulf at the pass of San Gorgonio, where the trains of the Southern Pacific Railway 

 cross the divide, and would make an island of the peninsula of Lower California. 



EVIDENCE OF UPLIFT. 



Such, no doubt, were the conditions in Middle Tertiary times. The waves of the Gulf 

 then washed the slope of the San Jacinto and San Bernardino, where we now find arid 

 mountains and desert plains. 



The silt of the Colorado was distributed far and wide in the interior sea, only partially 

 cut off from the broad Pacific by a chain of islands which now form the crest of the Penin- 

 sula Mountains from San Jacinto to Cape St. Lucas. As the land gradually rose from the 

 waves, the beds of oyster-shells and of other forms of marine life came into view and may 

 be seen to-day, 1,000 feet above the valley on the sides of the San Jacinto Mountains. 

 Such evidences of the former marine occupation of the valley are particularly strong and 

 convincing along the eastern base of the Peninsula Mountains, where marine fossils of the 

 Tertiary period are numerous, especially in the stratified formation along Carrizo Creek. 



