The further the conducta advanced in the direction of the mountains, the more difficult and dangerous the march became; the trees, at first scattered over a large space, became imperceptibly closer, and at last formed a dense forest, through which, at certain spots, they were compelled to cut their way with the axe, owing to the masses of creepers intertwined in each other, and forming an inextricable tangle; then again, there were rather wide streams difficult of approach, which the horses and mules were obliged to ford in the midst of iguanas and alligators, having frequently the water up to their girths. The immense dome of verdure under which the caravan painfully advanced, utterly hid the sky, and only allowed a few sunbeams to filter through the foliage, which was not sufficient entirely to dissipate the gloom which prevails almost constantly in the virgin forests, even at mid-day. Europeans, who are only acquainted with the forests of the old world, cannot form even a remote idea of those immense oceans of verdure which in America are called virgin forests. There the trees form a compact mass, for they are so entwined in each other, and fastened together by a network of lianas which wind round their stems and branches, plunging in the ground to rise again like the pipes of an immense organ, or forming capricious curves, as they rise and descend incessantly amid tufts of the parasite called Spanish beard, which falls from the ends of the branches of all the trees; the soil, covered with detritus of every sort, and humus formed of trees that have died of old age, is hidden beneath a thick grass several feet in height. The trees, nearly all of the same species, offer so little variety, that each of them seems only a repetition of the others. These forests are crossed in all directions by paths formed centuries agone by the feet of wild beasts, and leading to their mysterious watering-places; here and there beneath the foliage are stagnant marshes, over which myriads of mosquitoes buzz, and from which dense vapours rise that fill the forest with gloom; reptiles and insects of all sorts crawl on the ground, while the cries of birds and the hoarse calls of the wild beasts form a formidable concert which the echoes of the lagoons repeat. The most hardened wood-rangers enter in tremor the virgin forests, for it is almost impossible to find one's way with certainty, and it is far from safe to trust to the tracks which cross and are confounded; the hunters know by experience that once lost in one of these forests, unless a miracle supervene, they must perish within the walls formed by the tall grass and the curtain of lianas, without hope of being helped or saved by any living being of their own species. It was a virgin forest the caravan entered at this moment.