Periodical Literature. 87 



The amount of water evaporated annually from the oceans is 

 384.000 kur, equal to a depth of 106 cm. The precipitation over 

 the land area is calculated at 112,000 km^, equivalent to 75 cm 

 rainfall. The amount of water carried to sea by rivers is figured 

 at 30,640 krii^ (the flow of groundwater into oceans being neg- 

 lected). This is the surplus of precipitation over evaporation. 

 Adding the first two figures and deducting the last, 465,000 km^, 

 equivalent to 91 cm in height, is the amount of water which during 

 the year makes the circuit from earth and sea into the air and 

 back. There is a certain unmeasured addition of water vapor 

 which evaporated on land, contributes to the sea outside the river- 

 flow. This must be compensated for by a corresponding water 

 vapor inflow from the sea. 



The time which during this circulation a water particle in the 

 average ocupies in sea, air and land is speculated on. For the 

 maritime stage, the relation of the annually evaporated quantity 

 to the total water contents of the ocean can be used to figure. 

 The volume of ocean waters has been calculated at 1330 mill km^. 

 Of this evaporates the 3460th part; hence 3460 years in the aver- 

 age pass before any given water particle in the ocean passes into 

 the air. This is, of course, an average value ; while some particles 

 remain only a short time in the ocean, others may remain over 

 3,000 years before they come to be evaporated. 



To determine the time of suspension in the air, the air humidi- 

 ity values may be used, with the use of Hann's formula of the 

 vertical distribution of humidity. The water contents of the 

 total atmosphere are then found to be 12,300 km^, equivalent to a 

 precipitation of 24.2 mm. This, compared with the actual pre- 

 cipitation, (465,00 : 12,300) brings us to the conclusion that dur- 

 ing the year the atmosphere must discharge all the water it con- 

 tains 38 times during the year to furnish this precipitation, i. e., 

 a particle would have to return in the average in 9 to 10 days to 

 the earth ; those in the lower strata in a very much shorter time, 

 those in the upper strata in so much longer time. 



For the terrestial stage of the circulation, which interests us 

 the most, unfortunately the data are lacking. It would require 

 knowledge of the amount of water maintained in the soil, in ad- 

 dition to the amounts of snow and ice, which in that form retard 

 the water movement. 



