GEOGRAPHY AND ANTIQUITIES. 339 



EFFECTS OF THE REMOVAL OF FORESTS UPON CLIMATE. 



An interesting letter Avas recently read before the Geographical 

 Society of London, which shows the effects upon climate result- 

 ing from the clearing away of large tracts of forest. The facts 

 given are of universal interest. 



The paper was " On the Effects on Climate of Forest Destruc- 

 tion in Coorg, Southern India," Ipy Dr. Bidie. This district is 

 composed of hills and valleys, which were formerly covered with 

 forests. The lower slopes, however, are now denuded, and the 

 rainfall is found to decrease with the arboreal vegetation. As 

 regards the elevated crests of the Ghauts, which intercept the 

 rain-bearing winds of the south-west monsoon, they would cause 

 an abundant precipitation whether they were covered with trees 

 or not, but the water supply and fertility of tlio lower slopes and 

 plains to the east are seriously diminished by the clearing of 

 forest on the hills, and the result is brought about in the follow- 

 ing way : The natural forest acts as a check on the too rapid evapo- 

 ration, and carrying off by streams, of the rainfall on the surface 

 of the land. As the rain descends, it is gradually conveyed by 

 the leaves of trees to the dense undergrowth of shrubs, and carpet 

 of dead leaves, and below this it encounters a layer of vegetation 

 mould, which absorbs the water like a sponge. By these, aided 

 by the roots of trees, the moisture is transferred to the depths of 

 the earth, and a reservoir of springs is thus formed, which keeps up 

 a perennial supply of water to the lower land. But rain falling 

 on the bare surface of cleared lands runs oft" at once by the near- 

 est water-courses, and none is retained to keep up the flow during 

 the dry season. Beside which, evaporation is so much more 

 abundant from a surface exposed to the rain than from land 

 screened by a clothing of forest, and the flow of surface water 

 tends to sweep away the clothing of soil and render a district 

 utterly barren. There is no doubt that this is one of the main 

 causes, in hilly countries, of drought and floods. In France, for 

 instance, since the mountains of Auvergnc and Forey have been 

 so denuded of forests, the Loire has been constantly flooded, 

 occasioning vast destruction of property. The same cause, in 

 Algeria, has caused frequent droughts, and the French govern- 

 ment have lately been considering the proposition of some scien- 

 tific men to replant these districts with trees. 



THE MOUND-BUILDERS. 



In Dr. Foster's ** Mississippi Valley," the author gives an 

 account of the extent and distrilmtion of the relics of the ancient 

 Mound-Builders, a i-ace which, long antecedent to the North 

 American Indian, once occupied tlie region of the great lakes and 

 the valley of the Mississii)pi. Tiie trees which covered the 

 mounds when first discovered by the wliite settlers difiered in no 

 degree, either of size or form, from those of surrounding woods. 



