FORESTS AND THEIR CLBIATIC INFLUENCE. 413 



tliey form the Lake ofTacariguaor Yalenciaua, wbicli, at the time wheii 

 Ilumboklt saw it, liad been undergoing for some thirty years a gradual 

 desiccation, the cause of which was unknown. Oviedo, the historian of 

 Venezuela in the sixteenth century, relates that the city of Xueva Va 

 lencia was founded in 1555, at the distance of half a league from the 

 Lake of Tacarigua, from which, when Humboldt was there in 1800, it 

 was distant 2,700 toises, (3^- miles,) a proof of the retreat of the waters 

 confirmed by a number of facts. According to the celebrated traveler 

 just named, the diminution of the waters was directly attributable to 

 the clearing away of numerous forests. 



In 1822, M. Boussingault learned of the inhabitants that the waters 

 of the lake had exhibited a very sensible elevation; lands which were 

 before cultivated were then submerged. It is to be noted that, for the 

 term of twenty-two years previous, the valley had been the theater of 

 bloody contests during the war of independence ; the population had 

 been decimated, the lands had remained untdled, and the forests, which 

 grow with prodigious rapidity under the tropics, had eventually occu- 

 pied a great part of the country. TVe see here the influence of woods 

 ou the quantity of water which flows or settles in a country, since lakes 

 whicli had been exhausted by the removal of forests were again replen- 

 ished by their restoration. 



M. Boussingault cites several examples which lead to the same con- 

 clusion in regard to the influence exerted by great masses of wood on 

 the living waters of a country. "NYe shall quote two of the most remark- 

 able. In 1820, the metallifexous mountains of Marmato presented only 

 some miserable cabins inhabited by negro slaves. In 1830, this state 

 of things no longer existed ; there were numerous work-sliops aud a 

 population of 3,000 inhabitants. It had been found necessary to level 

 much wood : the denudation had proceeded but for two years, and already 

 a diminution was perceptible in the volume of water available for the 

 labor of the machines. Yet a pluviometer proved to M. Boussingault 

 that the quantity of water which had fallen in the second year was 

 greater than that which fell during the first. This fact tends to show that 

 disboscation may diminish and occasion the disappearance of sources, 

 though, from that circumstance, no inference is warranted of the fall of 

 a less quantity of rain. The second example is derived from the table- 

 lauds of Xew Grenada, at an elevation of from 2,000 to 3,000 metres, 

 (G,500 to 9,800 feet,) where there is a temperature during the whole 

 year of ll^ to 10°, (57^ to GIOF.) The inhabitants of the village of 

 Dubate, situated near two lakes, which were united sixty years ago, 

 have witnessed the gradual subsidence of the waters, insomuch that 

 lands which, thirty years since, were under water are now subject to 

 culture. The examination of local conditions and other investigations 

 made by M. Boussingault, convinced him that this change was due to 

 the disappearance of numerous forests which have been cut down. At 

 the same time other lakes, such as that of Tota, at a short distance from 

 Fuquene, situated in localities where the woods have been undisturbed, 

 have undergone no diminution of their waters. M. Desbassyres de 

 Eichemont has also discovered that there exists in the Island of Ascen- 

 sion, at the foot of a mountain, a fine water source, which became dry 

 in consequence of the denudation of the neighboring heights, but has 

 been restored since the forest was again allowed to grow. 



To complete the documents which may serve for the elucidation of 

 this question, there are still some importaut observations to be brought 

 forward. M. Berghaus {Cours (V Agriculture de M. de Gasparin, t. ii, p. 

 140) finds that the volume of water in the Oder and the Elbe undeiwent 



