30 ELEMENTARY FORESTRY. 



subject, I quote the following extract on forest influences from 

 the report of the Forestry Division of the U. S. Department of 

 Agriculture for 1889, with a few changes in the nature of abbre- 

 viations: 



"The water capital of the earth may be regarded as consist- 

 ing of two parts, the fixed capital and the circulating capital. 

 The first is represented not only in the waters on the earth but 

 also by that 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, remained in 

 suspension and is never precipitated. 



"The circulating water capital is that part which is evap- 

 orated from water surfaces, from the soil, from vegetation, and 

 which, after having temporarily been held by the atmosphere in 

 quantities locally varying according to the variations in tem- 

 perature, is returned again to the earth by precipitation in the 

 form of rain, snow and dew. There it is evaporated again, 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 through 

 open channels to the rivers and seas, continually returning in 

 part into the atmosphere by evaporation. Practically, then, the 

 total amount of water capital remains constant; only one part 

 O f it the circulating capital 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 

 no knowledge; hardly an approximate estimate of the amount 

 circulating in any given locality is possible with our present 

 means of measurement; for it appears that so unevenly is the 

 precipitation distributed that two rain gauges almost side by 

 side will indicate varying amounts, and much of the moisture 

 which is condensed and precipitated in dews escapes our obser- 

 vation, or at least our measurements, entirely. Thus it occurs 

 that while the amount of water calculated to be discharged 

 annually by the river Rhone into the sea appears to correspond 

 to a rainfall of 44 inches, the records give only a precipitation 

 over its watershed of 27.6 inches. 



