"Yes," said Ned, "that's it exactly, and we are now in an underground cavern. Don't be alarmed," he added quickly, noting the sudden pallor on his companion's face, "our situation is not so terrible after all. Caverns of this sort are always found among limestone hills, and they usually have two outlets. This one is no exception to the rule, and I'll tell you why I think so. In the first place you must remember that the creek was nearly four feet high before that dam broke. The extra volume of water is what makes this terrific current through the cavern and the very fact that the water goes on through without damming up proves to me that it has an outlet.