192 REPORT OF THE FORESTRY COMMITTEE 



lantic Ocean, the statement is not entirely correct. It is true that the southern 

 winds which prevail all over the eastern United States during the summer pass 

 over the Atlantic Ocean and the Gulf of Mexico and reach the land loaded with 

 moisture. As soon, however, as they reach the land part of the moisture is pre- 

 cipitated, and as they move farther inland they become drier and derive their 

 moisture more and more from the evaporation from the land. 



Of the 44,015,400 square miles of land surface of the earth, 79 per cent 

 drains directly toward the ocean and 31 per cent forms an inclosed inland area 

 without ocean drainage. The 79 per cent may be called the peripheral area of the 

 earth's surface, and the importance of the evaporation from it is, on the whole, 

 very great. 



PREVAIEING DIRECTIONS OF THE SURFACE WINDS AND THE MEAN PRECIPITATION IN 

 THE UNITED STATES DURING JANUARY. 



Prof. Ed. Briickner computes the "continental vapor" evaporated from this 

 peripheral area to be about 21,000 cubic miles (20,871.3 cubic miles). It plays, 

 therefore, even a more important part in supplying moisture to the air than does 

 the vapor directly evaporated from the ocean. Briickner estimates that the periph- 

 eral regions of the continents are capable of supplying seven-ninths of their pre- 

 cipitation by evaporation from their own areas. If the evaporation from land 

 plays such an important part in the precipitation over areas adjoining the ocean, it 

 becomes still more important at some distance from the ocean. It may be assumed, 

 therefore, that the moisture which is carried by the winds into the interior of vast 

 continents, thousands of miles from the ocean, is almost exclusively due to con- 

 tinental vapor and not to evaporation from the ocean. 



PREVAII^ING DIRECTIONS OF THE SURFACE WINDS AND THE MEAN PRECIPITATION IN 

 THE UNITED STATES DURING JULY. 



In the interior closed basins the precipitation and evaporation are, as a rule, 

 equal. 



The circulation of water on the earth's surface may be shOwn in the form of 

 a balance sheet as follows : 



