ITL— RELATION OF FORESTS TO AVATER SUPPLIES. 



By B. E. Feknow. 



THE TOTAI^ WATER SUPPLY. 



The water capital of the earth cousists of two parts, the fixed capital 

 and the circidating capital. The first is represented not only in the 

 waters on the earth, but also by the amount of water which remains 

 suspended in the atmosphere, being part of the original atmospheric 

 water masses which, after the rest had fallen to the cooled earth, re- 

 mained suspended and is never i)recipitated. 



The circulatiug water capital Ls that part which is evaporated from 

 water surfaces, froui the soil, from vegetatiou, and which, after having 

 temporarily been held by the atmosphere in quantities locally varying 

 according to the variations in temperature, is returned again to the 

 earth by precipitation in rain, snow, and dew. There it is evaporated 

 agaiu, either immediately or after having percolated through the soil 

 and been retained for a shorter or longer time before being returned to 

 the surface, or, without such percolation, it runs throngh open chan- 

 nels to the rivers and seas, continually returning in part into the 

 atuiosphere by eva])(»ration. Practically, then, the total auiount of 

 water capital remains constant; only oue part of it — the circulating cap- 

 ital — changes in varying quantities its location, and is of interest to us 

 more with reference to its local distribution and the channels by which 

 it becomes available for human use and vegetation than with reference 

 to its practically unchanged total quantity. 



As to the amount of this circulating water capital we have very 

 imperfect knowledge; in many cases an approximate estimate of the 

 amount circulating in any given area can not be satisfivctorily made 

 with the means of measurement at command, for often the precipitation 

 is so uuevenly distributed, as in the case of local thunderstorms, that 

 tNVo rain gauges a short distance apart collect varying amounts; hence 

 a record from one gauge alone would give a very erroneous idea of the 

 rainfall over the entire area. Furthermore, when improperly situated 

 or exposed to high winds a rain gauge may furnish quite inaccurate 

 records, and in the nuijority of cases the amounts collected by the 

 gauge will be iusutiicient. (See Trof. Abbe's paper in this bulletin.) 



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