178 
INFLUENCE ON PEECIPITATION. 
When, therefore, man destroyed these natural harmonizers 
of climatic discords, he sacrificed an important conservative 
power, though it is far from certain that he has thereby 
affected the mean, however much he may have exaggerated 
the extremes of atmospheric temperature and humidity, or, in 
other words, may have increased the range and lengthened the 
scale of thermometric and hygrometric variation. 
Influence of the Forest on Temperature and Precipitation. 
Aside from the question of compensation, it does not seem 
probable that the forests sensibly affect the total quantity of 
precipitation, or the general mean of atmospheric temperature 
of the globe, or even that they had this influence when their 
extent was vastly greater than at present. The waters cover 
about three fourths of the face of the earth,* and if we deduct 
the frozen zones, the peaks and crests of lofty mountains and 
* “ It has been concluded that the dry land occupies about 49,800,000 
square statute miles. This does not include the recently discovered tracts 
of land in the vicinity of the poles, and allowing for yet undiscovered land 
(which, however, can only exist in small quantity), if we assign 51,000,000 
to the land, there will remain about 146,000,000 of square miles for the 
extent of surface occupied by the ocean.”—Sir J. F. W. Herschel, Physical 
Geography , 1861, p. 19. 
It does not appear to which category Herschel assigns the inland seas 
and the fresh-water lakes and rivers of the earth; and Mrs. Somerville, 
who states that the “ dry land occupies an area of 38,000,000 of square 
miles,” and that “the ocean covers nearly three fourths of the surface of 
the globe,” is equally silent on this point .—Physical Geography , fifth 
edition, p. 30. On the following page, Mrs. Somerville, in a note, cites 
Mr. Gardner as her authority, and says that, “according to his com¬ 
putation, the extent of land is about 37,673,000 square British miles, inde¬ 
pendently of Victoria Continent; and the sea occupies 110,849,000. Hence 
the land is to the sea as 1 to 4 nearly.” Sir John F. W. Herschel makes 
the area of dryland and ocean together 197,000,000 square miles; Mrs. 
Somerville, or rather Mr. Gardner, 148,522,000. I suppose Sir John 
Herschel includes the islands in his aggregate of the “ dry land,” and the 
inland waters under the general designation of the “ ocean,” and that Mrs. 
Somerville excludes both. 
