One of our most interesting experiences was at the junction of the Rio Meta and the Orinoco, one hundred and fifty miles farther on, where we encountered the so-called “musical stones,” of which we had heard marvellous tales from the natives. These are granite cliffs which, we had been told, gave out at sunrise sounds closely resembling the tones of an organ. This mythical music, as we regarded it, caused us to stay here several days and finally, on one very cool morning, by placing our ears to the rocks, we distinctly heard subterranean growls, groans, and whistles, which could without great stretch of the imagination be compared to the notes of an organ, though it must needs be a wheezy one to make the similarity approximately honest. We all knew something about geology and, without pretending to give a scientific conclusion, it was our opinion that the sounds were caused by the hot air of the day, which the rocks retained during the night, being driven out by the cool air of the early morning through narrow fissures that were partially obstructed by thin layers of mica, lying at an angle to the general stratification, which served as reeds. The resultant vibrations were musical enough to produce a weird sensation as we listened to them, and it was easy to imagine the effect they would have on the ignorant and superstitious natives, and the stories for which they furnished a foundation. The Orinoco is navigable as far as the Meta for light-draft steamers at all seasons of the year, but it may be centuries before the “musical stones” become an advertised attraction for tourists. At Atures, one hundred miles above, and again at Maypures, just beyond, were two rapids around which our boats had to be carried; but with these exceptions it was plain sailing, or paddling, until we crossed the line into Brazil. Another hundred miles beyond the rapids brought us to the jumping-off place of the world--the indescribably filthy little hamlet of San Fernando de Atabapo, built where the Guaviare River comes down from the mountains of Colombia to join the Orinoco. It is on the border of Venezuela and Colombia and its population is largely made up of murderers and escaped convicts from both countries, with a few from near-by Brazil. A number of the leading citizens undertook to waylay us as we were leaving the place but the only result of their misguided effort was that two or three of them received what the law would have administered if it had been given a chance.