Probable Effects of Vegetation on Climate. 163 



left dry appearing the most fertile land in the neighbourhood. 

 This is ascribed by the distinguished traveller just named, to the 

 destruction of the trees on the mountains. When the war of 

 liberation broke out, agriculture was neglected, and the wood from 

 the hills was no longer required by human industry — a great 

 jungle began to prevail over all. The result was, that within 

 twenty years, not only had the lake ceased to subside, but began 

 once more to rise, and threaten the country with general inunda- 

 tion. This is only a single case out of many of precisely similar 

 nature with which South America supplies us. We have had 

 repeated occasion to allude to the diminution of rain in Oude, which 

 the older inhabitants compare to the retiring of the tide, so mani- 

 fest and gradual it is. In Switzerland it has been perfectly ascer- 

 tained, that rivulets formerly full have shrunk or dried up coincidently 

 with the denudation of the mountains, and that they have once more 

 returned to their former size on the woods being restored. A beauti- 

 ful spring, situated at the foot of a woody mountain in the island of 

 Ascension, was observed to diminish in flow as the trees were cut 

 down, and to vanish altogether when the wood disappeared. After 

 a few years, during which no water flowed, the mountain became 

 wooded again ; when the stream once more began to flow, and, as 

 the vegetation increased, returned to its former size. The destruc- 

 tion of wood, though at all times followed by a diminution in the 

 flow of running water, is not invariably attended by a decrease in 

 the fall of rain. Marmato, in the province of Popayan, is situate 

 in the midst of enormous forests, and in the vicinage of valuable 

 mines. The amount of the discharge of the streams, — here accu- 

 rately measured by the work performed by the stamping machines 

 which they drive, — was observed to decrease steadily as the wood 

 was cut down ; within the space of two years from the commence- 

 ment of the clearing, the decrease of the flow of the water had occa- 

 sioned alarm. The clearing was now suspended, and the diminution 

 ceased. A rain-gauge was now established, when it appeared that 

 the fall of rain had not diminished concomitantly with the flow of 

 the streams. The apparent anomaly here presented does not affect 

 the general doctrine, and is easily explained. The clearings were 

 too local to aff'ect the general condition of the climate ; the rain 

 which fell, however, instead of percolating, as was its wont through 

 the soil, when shaded by trees, producing springs, rivulets, and 

 brooks, now dried up, and was carried off in vapour as it fell. 

 India, in nearly all these things, furnishes precise parallels to South 

 America. A few years since a proprietor, in laying down some 

 ground well watered by an excellent spring, for a coffee garden at 

 Glenmore, in the Salem district, despite the advice of the natives, 

 cleared the ground, when the supply of water vanished. At the 

 village of Hoolbulley, near the head of the new Ghaut in Munze- 

 rabad, the jungle was cleared away, and in every case the diminution 



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