94 CARNEGIE INSTITUTION OF WASHINGTON. 



when it is intelligently sought for, and in connection with this search 

 it is possible that the considerations outUned above may prove of 

 practical value as well as of scientific interest. 



TJte Surface of the Painted Desert, by Godfrey Sykes. 



A brief reconnaissance has been made in the so-called Painted 

 Desert in Northeastern Arizona, supplementing cursory examinations 

 of the same region made 25 years ago. Superficially there are some 

 points of resemblance between this drainage area and that of the 

 Santa Cruz which render a simultaneous examination of the two 

 desirable. Both consist in the main of broad, open valleys, containing 

 typical desert rivers running from southeast to northwest; both areas 

 are comparatively arid and both are flanked by mountain ranges or 

 high plateaus. The resemblance almost ceases here, however, since, 

 owing to the general sandy and porous nature of the soil in the Painted 

 Desert, eoUan influences are far more potent in effecting topographical 

 change than they are in the Santa Cruz Valley, and vegetation is 

 much more scanty and its existence more precarious. 



The region is comparatively unexplored scientifically, and should 

 prove a most interesting one for the botanist, zoologist, and eremog- 

 rapher, from the fact that it consists in large part of a series of plat- 

 forms or terraces, extending parallel with the Little Colorado River 

 and isolated from each other by fairly well-defined cliffs or ramparts, 

 each possessing very distinctive features in soil and topography. 



Erosion in the Santa Cruz Valley, by Godfrey Sykes. 



During the past season the work of collecting data concerning the 

 physiography of the Santa Cniz drainage area has been carried on. 

 As a type of intermittent desert river the Santa Cruz affords many 

 features of the greatest interest. It has also undoubtedly served as a 

 channel for human intercourse from the earhest times, and since the 

 advent of the Spaniard in the Southwest its importance as such has 

 been very great. At present it is undergoing somewhat extensive 

 changes in the vicinity of Tucson, for it is in effect cutting through the 

 rim of a playa-like basin or bolson, in a temporary effort to render its 

 gradient more even. This effort has far-reaching effects upon vegeta- 

 tion, water-supply, and kindred matters, and is therefore of consider- 

 able scientific interest. The examination of the valley in its entirety 

 has been hampered, however, by the chaotic conditions across the 

 Mexican border, as, although rising in Arizona, the river makes a 

 greater detour through the Mexican State of Sonora before assuming 

 its main course towards the northwest. 



