1849.] On the Influence of Forests on Climate. 797 



important functions, and are as indispensable in the economy of nature 

 as the liquid air which encircles our globe, or the mighty ocean which 

 lashes its shores. 



" The carbonic acid with which our breathing fills the air, to-morrow 

 will be spreading north and south and striving to make the tour of the 

 world. The date trees that grow round the fountains of the Nile will 

 drink it in by their leaves ; the Cedars of Lebanon will take of it to 

 add to their stature, the cocoa-nuts of Tahiti will grow riper upon it, 

 and the palms and bananas of Japan will change it into flowers." 



" The oxygen we are breathing was distilled for us some short time 

 ago by the magnolias of the Susquehanna and the great trees that 

 skirt the Orinoco and the Amazon. The giant rhododendrons of the 

 Himalayas contributed to it, the roses and myrtles of Cashmir, the 

 cinnamon trees of Ceylon, and forests older than the flood, buried 

 deep in the heart of Africa far behind the mountains of the moon. 

 The rain which we see descending was thawed for us out of icebergs 

 which have watched the polar star for ages, and lotus lilies sucked up 

 from the Nile and exhaled as vapour the snows that are lying on the 

 tops of our hills."* 



Among the many causes which produce certain modifications in the 

 climate of any region, and one which is too frequently overlooked, 

 is the nature of the soil. This is principally owing to the greater or 

 less power any soil possesses of radiating heat. Thus sandy soils are 

 subject to become rapidly and intensely heated, and when the rays of 

 the sun are withdrawn, they readily radiate or impart to the atmo- 

 sphere the heat they have acquired, thus increasing the general tem- 

 perature. Clayey soils on the other hand become slowly heated, and as 

 slowly part with heat ; swampy ground chills the air, and extensive 

 forest tracts have a similar effect. And thus cultivation not unfre- 

 quently effects a change in the climate of a country, for if marshes are 

 drained, or forests cleared, the temperature will be raised. It thus 

 appears that the diversities of climate are brought about by various 

 causes, and are chiefly dependant on latitude ; on the distribution of 

 land and water ; on the elevation of land above the sea, as also on the 

 nature of the soil, the prevalence of particular winds, and position of 

 forest, on currents of the ocean, on the direction and extent of moun- 

 tain ranges, and many other local circumstances. 

 * British Quarterly Mag. 



