The Utility of our Victorian Forests. 407 



the rainfall, regulation of moisture, and the healthiness of countries. 

 In modern times observations on the most accurate basis have been 

 undertaken, in Europe, America, and India, to prove effects of forests 

 on temperature and rainfall. The system adopted was to have an 

 observation station situated in the forest under the shade of high 

 trees ; another station outside the forest, in the open, and at some 

 distance from it. The readings were taken two and three times a day, 

 and in two cases, every hour. The results proved, that on the whole, 

 the forests slightly reduced the temperature of the air. It also 

 proved that the difference in temperature was greatest in summer, 

 least in winter, and about equal in spring and autumn, also that the 

 temperature of the forest was higher during the night, and lower 

 during the day, than on open ground, this last difference was most 

 pronounced during summer. 



Terrvperature of the Soil. — The temperature of the soil is governed 

 by that of the air, and the conclusions arrived at were, that the mean 

 annual temperature was nearly the same from 1 foot to 4 feet down, 

 and that the mean annual temperature of the forest soil is decidedly 

 lower than that of soil in the open, in summer by nearly 7 degrees, but 

 very little in winter. The effect differs also in dift'erent species of 

 forest, an evergreen forest showing a greater reduction in temperature 

 than a deciduous. From the foregoing we may conclude that the 

 climate in forest countries is more equable than in open countries, 

 and the temperature of soil and air in forests is slightly lower than 

 in open countries, while vegetation starts later in forests than in the 

 open. 



Hot countries may benefit by forests, but those countries removed 

 from the equator may suffer where the temperature is already lower 

 than is good for field crops. Plants grown in the open, suffer more 

 from drought, and early and late frosts than those grown in forests. 



The Moisture of Air. — Science teaches us that air can only hold 

 a. certain quantity of vapour — this increases and decreases with the 

 temperature. When more than the maximum is reached, it becomes 

 ffuid. The vast sheets of water that cover the earth's surface 

 govern, to a great extent, the humidity of the air; still the forest 

 vegetation must exercise an effect, owing to the reduction of 

 temperature within its sphere of influence. Careful experiments go 

 to show that the mean annual excess of humidity in forests ranged 

 from 8 to 10 per cent, and it is a known fact that a dry current of air 

 passing through a forest becomes moist ; so much so, that precipita- 

 tions may be caused. Dew is also formed in greater quantities near 

 a forest than away from it. 



Rainfall. — The much discussed question as to how far forest 

 growth can or does influence rainfall remains still unsolved. It is an 

 undisputed fact that forests can affect precipitations, since forest-air 

 is moister than air in the open, and the trees do affect the movement 

 of air. But rainfall depends chiefly on other more powerful agencies, 

 compared to which, the forests powers ai'e but small. Elevation 



