. Carnegie Institution of Washington publication. 58 VEGETATION OF A DESERT MOUNTAIN RANGE. INCHES 30 i higher elevations are derived from a higher cloud level, probably from convectional clouds which form at times when the atmospheric con- ditions cause condensation at a greater distance from the earth. When a long series of records shall have been secured from the 9,000-foot station it will probably show that its average rainfall is greater than that at 8,000 feet, but the 9,000-foot record for 1913 indicates that there will be occasional years, at least, in which the maximum for the mountai
. Carnegie Institution of Washington publication. 58 VEGETATION OF A DESERT MOUNTAIN RANGE. INCHES 30 i higher elevations are derived from a higher cloud level, probably from convectional clouds which form at times when the atmospheric con- ditions cause condensation at a greater distance from the earth. When a long series of records shall have been secured from the 9,000-foot station it will probably show that its average rainfall is greater than that at 8,000 feet, but the 9,000-foot record for 1913 indicates that there will be occasional years, at least, in which the maximum for the mountain is recorded at 8,000 feet. This probably means that at 10,000 feet on adjacent mountains there is a constantly lower rainfall than at 8,000 or 9,000 feet. The check in the vertical increase of rainfall which has been described as occurring between 4,000 and 6,000 feet appears to be absent from all curves derived from widely separated valley stations. The writer has seen no such plateau in any curves derived from southwest- ern data, but there is always the possibility that a plateau has been smoothed out of the curves or that the data have been sub- jected to the influence of a straight-line equation. The character of the increase of pre- cipitation with altitude in a sin- gle small range of mountains is no more a special case than is the increase in a widely separated series of stations in any locations whatsoever. In so far as con- cerns the study of meteorological dynamics, such a mountain range as the Santa Catalinas offers exceptional opportunities for investi- gation, and much more might be learned in a single summer of intensive meteorological study on its slopes than could be ascertained by an exami- nation of records of rainfall covering a period of a thousand years. As regards vegetation, the most important feature of the study of rainfall conditions is the determination of the extremes of variation in the amount and seasonal distribution of rain, and the ascertaini
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