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The gully (or arroyo) in the American Southwest has attracted scientific attention for more than three score years. In the first phase, gullies tended to be viewed as the result of changes in the vegetation cover brought about by man and his live-stock. Later, the discovery of prehistoric gullies led to a shift of attention to possible climatic causes and to the elaboration of a widely accepted model relating climatic events to erosion-deposition. In the last five years, the study of the pollen record has inspired a new model of interpretation, different in important respects from the older one, The examination of New Mexican gullies suggests that the new model has certain advantages, but that in fact our knowledge is still extremely hypothetical. Lacking is a detailed comparison of the local environments under which erosion-deposition takes place, and lacking also is a documented history of the gullies. An attempt is made to compare the local environments of gullies in New Mexico and, in the case of the Rio Chaco and the Rio Puerco, to document the history of their gullies in some detail.

The relationship of climate to land-surface morphology and genesis has been investigated by numerous writers for well over half a century. Such studies have focused in part upon interpreting erosional cycles, but more importantly they have to an increasing degree been oriented toward understanding the areal variation of specific surface forms and geomorphic processes. Especially pertinent to the geographer are recent attempts in the United States, and particularly by Julius Büdel in Germany, to use climatic influence as a basis for establishing morphogenetic and climato-genetic regions. [ABSTRACT FROM AUTHOR]

Reports on the factors influencing the failure of wheat, a crop of dry farming in Nebraska. Record of agricultural experiment farms; Climatic changes; Increase in the use of summer fallow.

Examines runoff and soil moisture in the desert conditions of Arizona. Influence of rainfall on physiographic processes; Facts about the rainfall of the Tucson region in Arizona; Data on the average annual rainfall; Distribution of precipitation; Implications of the irregularity of rainfall in southern Arizona; Occurrence of drought; Determinants to the amount of runoff.

Examines special maps for charting storm movements in the U.S. Fundamentals of aerography; Assessment of the structure of atmosphere in general and sequence of weather changes; Evaluation of the lines of equal pressure.