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PHYSICAL GEOGRAPHY. 



of Franconia, the Ilartz and Carpathian mountains ; and the uniformity generally observ 

 able in all these, led him to expect a scene of a similar character in that which he 

 explored in the New World : but the reality far exceeded his expectations ; for, if the 

 structure of the cave resembled those he had elsewhere witnessed, the majesty of equinoc 

 tial vegetation gave an individual character and indescribable superiority to the entrance 

 of the Cavern of the Guacharo. The entrance is a vaulted arch, eighty feet broad and 

 seventy -two feet high; the steep rock that surmounts this opening is covered with 

 gigantic trees, mixed with creeping and climbing plants and shrubs, brilliant with blos 

 soms of the richest colours and the most varied forms. These form natural festoons, 

 which hang from the mouth of the cave, and are gently agitated by the passing currents 

 of air. Among them Humboldt enumerates a Dendrobium, an orchideous plant, with 

 golden flowers spotted with black, and three inches long ; a Bignonia, with a violet blos 

 som ; a purple Dolichos ; and a magnificent Solandra, the deep orange flower of which has 

 a fleshy tube four inches long. But this luxuriant vegetation was not alone confined to 

 the exterior. The traveller, on following the banks of a subterranean stream into the 

 grotto, beheld them, with astonishment, adorned for thirty or forty yards with the Praga 

 palm tree, plantain-leaved heliconias, eighteen feet high, and arms that resembled trees in 

 their size ! It was not found necessary to light their torches till they had reached the 

 distance of 430 feet, owing to the continuous direction of the cavern, which allows the 

 light of day to penetrate thus far ; and when this began to fail, the hoarse cries of the 

 nocturnal birds began to be audible from a distance. The shrill discordant noise made 

 by thousands of these birds, brought from the inmost recesses of the cave, and rever 

 berated from the arched roofs, formed an indescribable clamour. The Indian guides, by 

 fixing torches to the ends of long poles, showed the traveller the nests of the bird, which 

 were constructed in funnel-shaped holes, with which the roof of the grotto was pierced in 

 all directions, and generally at about sixty feet high. Still pursuing the course of the 

 river, the cavern preserved the same width and height to the distance of 1458 feet from 

 the mouth. The traveller, on turning round, was struck with the singularly beautiful 

 appearance which a hill covered with the richest vegetation, immediately fronting the 

 entrance of the grotto, presented. This, brilliantly illumined by the sun's rays, and seen 

 through the vista of the dark cave, formed a striking contrast to the surrounding ob 

 scurity ; while the large stalactites depending from the roof were relieved against the lumi 

 nous back-ground of verdure. After surmounting, with some difficulty, an abrupt rise in 

 the ground where the stream forms a small cascade, he found that the cave diminished in 

 height to forty feet, but retained its original direction. Here a blackish mould was 

 found, either brought by the rivulet, or washed down from the roof by the rain-water 

 which penetrates the crevices of the rock ; and in this he found seeds growing, which 

 had been brought thus far by the birds, but so altered by the deprivation of light, that 

 the species of plant, thus produced under such unfavourable circumstances, could not 

 even be recognised. It was found impossible to persuade the Indian guides to advance 

 further. The cries of the birds, rendered still more horrible by the contraction of the 

 cave, had such an effect on their minds, that they absolutely refused to proceed ; and, to 

 the regret of Humboldt, he was compelled to retrace his steps. 



Caverns, especially those which are situated in limestone, commonly present the 

 formations called stalactites, from a Greek word signifying distillation or dropping. The 

 manner of their production admits of a very plain and simple explanation. They proceed 

 from water trickling through the roofs containing carbonate of lime, held in solution by 

 carbonic acid. Upon exposure to the air the carbonic acid is gradually disengaged, and 

 a pellicle of lime is deposited. The process proceeds, drop after drop, and, eventually, 

 descending points hanging from the roof are formed, resembling icicles, which are com- 



