CAUSES OF THE DESERT — CLIMATE — WELLS, 



127 



The Colorado desert is an extended plain, unbroken by an eminence of any great height, 

 (save the lone hills,) and may be considered as an ancient sea bottom, with raised terraces here 

 and there, loose sand hills, 30 feet high in some places, fine moving sand, 2 inches deep, strewed 

 over aflat, clay bottom, with here and there aggregations of small drift stones, granite, porphyry, 

 trachyte, and quartz, polished smooth by the sand ; acres without a bush or blade of grass, 

 and, elsewhere, a scattered growth of greasewood, creosote tree, wild sage, mesquite, and 

 fouquieria. It might be interesting, though hardly in place here, to enter into all the causes 

 which have rendered and keep this still a desert. 



It is notorious that a desert tends to propagate itself by its shifting sands covering up good 

 soil, and by the destruction of the humus or organic matter so needful for vegetation. When 

 humus is absent from a soil, it becomes too much heated or too much cooled by absorption and 

 radiation, and all moisture is effectually removed. Shade and moisture are necessary to repro- 

 duce humus from vegetation, but as these do not exist on the desert, it is eternally perpetuated 

 a naked sand or clay. 



An elevated mountain range to the west, a basin nearly at sea level, and an almost intertro- 

 pical latitude, are the circumstances which conspire to form a desert there. Tlie first, by its 

 height, elfectually drains the clouds, so that but little rain falls eastward — hardly ever more than 

 two inches in the year. 



The second, by its configuration and depression, favor the concentration of the solar rays, 

 making it the focus of a large area. 



The last has an influence not less than the others ; in parallel 32 there are no large timber 

 trees ibund in low situations ; it is also too warm for the growth of the ordinary grasses, so that 

 shade and the protection of the ground necessary for the production of humus do not exist ; 

 additional moisture is required ; irrigation and the cultivation of trees, shrubs and fruits of the 

 continent further south, which would bear transplantation, would convert portions of this desert 

 into a fertile country. 



OF THE CLIMATE AND WATER SUPPLY OP THE DESERT. 

 The following is a tabular statement of the principal water stations between the eastern slope 

 of the Sierra and Fort Yuma, with the intermediate distances and the character of the water at 

 each station. Having touched at Sackett's wells, makes the distance from station to station 

 somewhat different from the table given by Mr. Williamson. 



The mode of obtaining water, and the amount of supply, from each of these points has been 

 already alluded to. There is a melancholy neglect for the comfort and safety of men and 



