218 INFLUENCE OF THE FOEEST ON SPRINGS. 



no outlet to the ocean, form, by tlieir nnion, tiie Lake of Tacari- 

 gua or Valencia, having a length of about two leagues and a half 

 [= Y English miles]. 



" At the time of Humboldt's visit to the valley of Aragua, the 

 inhabitants were struck by the gradual diminution which the lake 

 had been undergoing for thirty years. In fact, by comparing the 

 descriptions given by historians with its actual condition, even 

 making large allowance for exaggeration, it was easy to see that 

 the level was considerably depressed. The facts spoke for them- 

 selves. Oviedo, who, towards the close of the sixteenth century, 

 had often traversed the valley of Aragua, says positively that 

 iJ^ew Yalencia was founded, in 1555, at half a league from the 

 Lake of Tacarigua ; in 1800, Humboldt found this city 5,260 

 metres [^3^ English miles] from the shore. 



" The aspect of the soil furnished new proofs. Many hillocks 

 on the plain retain the name of islands, which they more justly 

 bore when they were surrounded by water. The ground laid 

 bare by the retreat of the lake was converted into admirable 

 plantations ; and buildings erected near the lake showed the sink- 

 ing of the water from year to year. In 1Y96, new islands made 

 their appearance. A fortress built in 1Y40 on the island of Ca- 

 brera, was now on a peninsula ; and, finally, on two granitic isl- 

 ands, those of Cura and Cabo Blanco, Humboldt obseiwed among 

 the shrubs, some metres above the water, fine sand filled with 

 helicites. 



" These clear and positive facts suggested numerous explana- 

 tions, all assuming a subterranean outlet, which permitted the dis- 

 charge of the water to the ocean. Humboldt disposed of these 

 hypotheses, and did not hesitate to ascribe the diminution of the 

 waters of the lake to the numerous clearings which had been 

 made in the valley of Aragua within half a century." 



Twenty-two years later, Boussingault explored the valley of 

 Aragua. For some years previous, the inhabitants had observed 

 that the waters of the lake were no longer retiring, but, on the 

 contrary, were sensibly rising. Grounds, not long before occu- 

 pied by plantations, were submerged. The islands of JN^uevas 

 Aparecidas, which appeared above the surface in 1796, had again 

 become shoals dangerous to navigation. Cabrera, a tongue of 

 land on the north side of the valley, was so narrow that the least 



