The opening to the tunnel was much as Andrew had described it, an inconspicuous, narrow rift at the base of a great wall of rock. In nine cases out of ten it would pass unnoticed; so small an aperture, concealed by bushes and trailing vines, was safe from the most inquisitive travelers. That so timid a person as the schoolmaster had discovered (no one took seriously his tale of the togaed and sandaled stranger) and forced his way through this opening caused no end of wonder. To accomplish the same feat drew forth many a groan from the corpulent Leighton and Miranda. As for Mrs. Quayle, what with the squeezing and tugging needed to gain an entrance into the region of terrors beyond, and anxiety lest some of her jewelry might be lost in such strenuous effort, that good lady came dangerously near a condition of hopeless panic. Undoubtedly she would have abandoned the expedition then and there had it not been for the jeers of Miranda who assured her she was developing symptoms that called for a generous dose of his infallible pills. Such a goad would electrify the stubbornest of mules and a series of desperate struggles brought Mrs. Quayle victoriously through the tunnel's entrance. This first step in their subterranean travels surmounted, the explorers, having lighted their lamps, found themselves in a spacious rock chamber, the walls of which rose above them to a majestic height. Andrew, especially, was amazed at what he saw, declaring that it was all quite different from his first experience in the same place. When it was remembered, however, that on this former occasion the schoolmaster had only the feeble glimmer of light that found its way through the opening of the cave to show him where he was, the difference between his two impressions was not surprising. But it puzzled his companions to choose the route they were to follow in their explorations. Here Andrew could not help them. Two passages were discovered leading from the chamber in which they stood. One went straight ahead, offering a fairly easy, unobstructed path to the explorer. The other, a branch from the main tunnel, was narrow, strewn with debris of fallen rock, and altogether forbidding in the glimpse that could be had of the first few hundred feet of its course. One feature, however, belonging to this smaller tunnel gave it the preference. But before discovering this feature and making their choice the explorers thought it best to inform themselves, as well as they could, of the character of the cave itself. In this Leighton naturally took the lead, and from his investigations it was concluded that, unlike other caves, the origin of the Guatavita cave was primarily volcanic and due only secondarily to the action of water.