MOVEMENTS OF VEGETATION IN THE SALTON SINK. 117 



A year later a second expedition, starting 300 miles up the Colorado, was made down 

 through the Delta, returning to the northward along the western margin of the alluvial 

 lands. 1 



The southernmost of the canal intakes had been eroded deeper and wider by the inflow- 

 ing current and a stream large enough to float a steamer flowed through it to the westward, 

 spreading out over the alluvial lands, but finally collecting in two main channels known 

 as New River and Alamo River leading down into the Sink. New River was crossed at 

 Calexico in small boats, and it was at this time simply a muddy stream a few feet in depth, 

 but the water was nearly level with the banks. Later, as is noted elsewhere in this volume, 

 a great amount of erosion occurred which excavated a deep and wide channel. Returning 

 to the main line of the Southern Pacific Railway the Alamo was crossed, but no special 

 observations were made on its flow. 



A party from the Desert Laboratory proceeded southward from Mecca to Travertine 

 Rock in May 1906, and made an examination of the shore of the lake, which at this time 

 had attained a maximum depth of 34 feet, with a total area of nearly 300 square miles. 

 The party included Professor W. P. Blake, who made the trip to verify his observations 

 of 1853 upon the travertine formations which had been observed by him fifty-three years 

 earlier. (See Plate 1 b.) Samples of the water were taken (see page 35) and the shore phe- 

 nomena were observed. The scope of the opportunities for research upon several geographi- 

 cal problems was recognized and comprehensive plans for dealing with the entire matter were 

 formulated during the year. 2 



The inflow of the water proceeded, but early in 1907 the engineering operations of 

 the Southern Pacific Railway promised to close the breaks and place the inflow under 

 control, and a small sailboat was constructed at Mecca early in January for purposes of 

 exploration. A party with full field equipment embarked in this boat for a trip around the 

 shores of the lake and to the islands on February 7, and made daily camps ashore during 

 the following ten days. The highest level of the lake with a maximum depth of 84 feet 

 was reached on February 10, at which time the party was camped near the southern end 

 among the great crescentic dunes of the Carrizo sands. During all of this voyage landings 

 were made with the greatest difficulty, as the steady rise of the lake had simply pushed a 

 sheet of water out over the loose alkaline soil of the desert and made a soft mud into which 

 one would sink to a depth of 2 or 3 feet in a few seconds, and the saturated soil would be 

 moist and soft for some yards away from the water. Long tongues of water extended far 

 up the channels of the dry washes and no true beaches or strands had yet been formed by 

 the sorting or solidification of the soil material. (See Plate 12 c.) So rapidly had the level 

 risen that several of the great crescentic dunes had been surrounded by water and their 

 long ridges still showed above the water like curved whale-backs. (See Plate 12 b.) Thou- 

 sands of rounded masses of pumice, from 1 to 6 inches in diameter, floated on the surface, 

 as well as many of the hard-shelled globular fruits of Cucurbita palmata. The water at 

 this time contained about 0.25 per cent of dissolved salts, which is near the limit of pota- 

 bility. This was denoted by the fact that it could be used by some members of the party, 

 but not by others. 



Four hills in the southeastern part of the basin stood above the water as islands. The 

 southernmost was known as Big Island and rose in conical form to a height of over 100 feet 

 and showed the terraces of previous lake formations far above the recent level. (Plate 6 d.) 

 Its base was fringed by lower flattish hills on the southward, separated from it by narrow chan- 

 nels, and the recession of the waters rapidly increased the exposed area, while the top of a hill 

 to the northward came above the water in 1908. (Plate 6 d.) Rock Island was the crest of a 



1 MacDougal, D. T., Botanical explorations in Arizona, Sonora, and Baja California. Journal of N. Y. Bot. Garden, 



vol. vi, p. 91, 1905. 



2 Report of Department of Botanical Research for 1906, Year Book Cam. Inst. Wash., No. 5, 1906. 



