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THE NATIONAL GEOGRAPHIC MAGAZINE 



cases far in the distance, and as a result 

 seen a dry wash suddenly fill with a 

 stream 20 feet deep advancing in suc- 

 cessive high waves. The flow would last 

 .a few hours, rapidly subside, and per- 

 haps the wash w^ould not be a water 

 vcourse again for several years. 



The several large rivers that flow 

 across deserts of the southwest accumu- 

 late their waters from melting snows and 

 iheavy rainfall in distant high mountains. 



The temperatures in the deserts of the 

 :Southwest rise high in midsummer, often 

 -attaining 125 degrees in the lower lands 

 •of Death Valley and the lower Colorado 

 Valley. 



The desert vegetation is always a 

 :source of interest to the traveler, espe- 

 'Cially the varied and conspicuous cactus 

 flora. The Sagu3.r0 (Ccreiis gigaiifeuni) 

 'Of central and southern Arizona (page 

 '651) is one of the most notable forms. 

 It lives in areas where the precipitation 

 is only three or four inches a year, but 

 is restricted to the warmer districts. It 

 "has wonderful capacity for rapid ab- 

 :Sorption of a large amount of moisture, 

 whether from a heavy downpour or a 

 •slight dampening. 



The biznaga {BchinocacUis emori), 

 .also known as watermelon or barrel cac- 

 tus, is an associate of the Saguaro, and I 

 ■can add my testimony to its usefulness 

 .as a most important water bearer. By 

 •cutting oflf its top and beating up the 

 pulp with a stick one can secure a draft 

 of watery juice of fair flavor which will 

 effectively quench the desert thirst. 



I once spent the month of November 

 in the deserts of southeastern California 

 investigating artesian waters for the 

 ;Santa Fe Railroad, and the experience 

 was one of the most delightful of my 

 life. The climatic conditions were per- 

 fect, and the region was full of novel 

 features of geology, flora, physiography 

 .and scenery which kept me greatly in- 

 terested throughout the trip. 



One must live awhile in the desert to 

 realize its many charms. The brilliant 

 sunsets are especially impressive, and the 

 .glowing twilights foflowed by marvelous 



eflfects of light and shade at nightfall 

 piles great velvety shadows along the 

 slopes of the mountains. 



The Southwest, however,* is rich in 

 features that interest even the most 

 casual observer. The most notable is 

 the Grand Canyon of the Colorado, 

 which is in many ways the greatest 

 natural wonder in the world. 



the: grand canyon 



This canyon is the mile-deep gorge 

 cut by the Colorado River across the 

 high plateau of northern Arizona. The 

 view from the rim reveals the most stu- 

 pendous panorama imaginable, for one 

 sees into an area of about 600 square 

 miles filled with an endless variety of 

 most rugged topographic forms of many 

 beautiful colors. On the sky-line, 10 to 

 15 miles away, is the edge of a wide- 

 reaching plateau, and in the middle 

 ground of the picture flows the Colorado 

 River, nearly a mile below one's feet. 



The features are so gigantic and so 

 plainly in view that all sense of scale is 

 lost, and it is not until one has been 

 down to the bottom of the canyon at the 

 river level that any adequate sense of 

 proportion can be gained. 



It is not a smooth-walled canyon of 

 simple type, for, instead, the descent is 

 by a succession of great cliffs and long, 

 steep slopes, and the walls are an alter- 

 nation of deep recesses and far-reaching 

 promontories. Some of the latter are 

 several miles long, and broken into irreg- 

 ular buttes of many forms. 



The canyon is a most superb illustra- 

 tion of direct erosion, for the primary 

 agency in its formation has been flow- 

 ing water. The movement of talus 

 down slopes, the action of frost, and the 

 sculpturing by wind-blown sand have 

 had an influence in the final details. Cer- 

 tain differential earth movements — faults 

 and flexing — have also caused some mod- 

 ifications of contour. The configuration 

 of the features in the canyon are closely 

 related to rock texture ; the great cliffs, 

 many of them 600 feet high, and the 

 plateau, are due to nearly horizontal 

 limestones and sandstones of very mass- 



