330 ANNUAL OF SCIENTIFIC DISCOVERY. 



to split ; while the aged and unyielding trunks of aged trees are those 

 that suffer most in this way. Some facts are cited to show that the 

 splitting and rending of trees by freezing is occasioned by the unequal 

 contraction of the layers of wood caused by a sudden application of 

 cold ; for observation leads to the belief that the congelation of the sap 

 alone does not produce this effect. 



In conclusion, it must be admitted that the analogy between plants 

 and animals is very perfect. There are genera of both, in which all the 

 fluids may be frozen without perceptible injury, while both appear to 

 be able to withstand a high degree of cold in a dormant state. 



PROBABLE EFFECTS OF VEGETATION ON CLIMATE. 



IN the Secretary's report of the proceedings of the Bombay Geo- 

 graphical kSociety, for 1850, some interesting facts are given in regard 

 to the influence of vegetation on the amount and distribution of moist- 

 ure, and the consequent effect on climate. 



It was early remarked by Humboldt, that men in every climate, by 

 felling the trees that cover the tops and sides of mountains, prepare at 

 once two calamities for future generations the want of fuel and a 

 scarcity of water. Trees, by the nature of their perspiration, and the 

 radiation from their leaves in a sky without clouds, surround them- 

 selves with an atmosphere constantly cold and misty. They affect the 

 copiousness of springs, not, as was long believed, by a peculiar attrac- 

 tion for the vapors diffused through the air, but because, by sheltering 

 the soil from the direct action of the sun, they diminish the evapora- 

 tion of the water produced by rain. When forests are destroyed with 

 an imprudent precipitation, as they are everywhere in America, the 

 springs entirely dry up, or become less abundant. The beds of the 

 rivers, remaining dry during a part of the year, are converted into tor- 

 rents whenever great rains fall on the heights. The sward and the 

 moss disappearing with the brushwood from the sides of the moun- 

 tains, the waters falling in rain are no longer impeded in their course ; 

 and, instead of slowly augmenting the level of the rivers by progressive 

 filtration, they furrow, during heavy showers, the sides of the hills, 

 bear down the loosened soil, and form those sudden inundations that 

 devastate the country. Hence it results, that the destruction of forests, 

 the want of permanent springs, and the existence of torrents, are three 

 phenomena closely connected together. In India, their effects are very 

 appreciable. At Dapoolie, the climate is much more hot and dry than 

 formerly ; streams now dry up in December which used to flow until 

 April or May. This is attributed to the destruction of forests which 

 formerly covered the neighboring hills, now barren and desolate. In 

 southern Coucan, within the space of fifteen years, the climate has 

 been greatly deteriorated by the diminution of vegetation and conse- 

 quently of rain. The people of Pinang have memorialized government 

 against the destruction of their forests, feeling sure that the result by 

 its continuance will be the ruin of the climate. The dreadful droughts 

 which now so frequently visit the Cape de Verd Islands are avowedly 

 due to the removal of their forests ; and in the high lands of Greece, 



