104 THE DESICCATION OF LATER GEOLOGICAL TIMES. 



it being Captain Stansbury's idea, apparently, that the mountains surround- 

 ino- the hike had been elevated, and not that the lake itself had diminished, 

 so that its water surface now stands at a lower level than formerly. 



The geologists of the various Pacific railroad surveying expeditions paid 

 little attention to the proofs of a gradual drying-up of the region under ex- 

 amination, and when they did observe them, they seem to have failed to 

 apprehend their true character. Thus Lieutenant Beckwith remarks, in 

 speaking of the terraces bordering Great Salt Lake : " They are elevated 

 from two or three hundred to six or eight hundred feet above the present 

 lake ; and if upon a thorough examination they prove to be ancient shores, 

 they will perhaps afford (being easily traced on the numerous mountains of 

 the Basin) the means of determining the character of the sea by which they 

 were formed, whether an internal one, subsequently drained off by the break- 

 ing or wearing away of the rim of the Basin, — of the existence of which at 

 any time, in the form of continuous elevated mountain chains, there seems 

 at present but little ground for believing, — or an arm of the main sea, 

 which, with the continent, has been elevated to its present position, and 

 drained by the successive stages indicated by the shores."* 



Mr. W. P. Blake, who Avas attached to the party which explored the south- 

 ern portion of California, and whose geological investigations are contained 

 in the fifth volume of the Pacific Railroad Reports, published in 1856, noticed 

 the former existence of " an extensive fresh-water lake " in the northern part 

 of the Colorado Desert, by which term he designates the tract of country 

 lying between the Bernardino Range on the northeast and the San Jacinto 

 Mountains, and the connected ranges extending towaid the southwest along 

 the Pacific Coast. The area thus embraced within these lofty mountains is 

 about 120 miles in length, narrow at its northern extremity, where it is 

 called the Coahuila Valley, but widening out rapidly towards the south, and 

 meeting the Colorado River near Fort Yuma. This region is almost destitute 

 of water, the streams which find their way down the mountain slopes losing 

 themselves before reaching the valley. A considerable portion of this area is 

 depressed below the sea-level, as shown by the recent surveys for the South- 

 ern Pacific railroad, and there are abundant evidences, in the form of terraces, 

 ancient shore-lines, and deposits of calcareous matter at various points, that 

 the water of the Gulf of California once extended up nearly' to the head of 

 Coahuila Valley. The access of the sea having been cut ofl' by the accumu- 



* Keport of Exploiatiuiis and Surveys, etc. (Pacific Kailroad Ec^iorts). Washiiigtou, 1S55, Vol. II. p. 97. 



