"Pretty deep, Tommy. But we can get an idea by dropping a stone and counting the seconds until it strikes." * * * * * He played the light of the flash over the floor and soon located a smooth round stone of the size of a baseball. This he tossed over the rim of the pit and awaited results. "Good grief!" exclaimed Tommy. "It's not falling!" What he said was true, for the stone poised lightly over the opening and drifted like a feather. Then slowly it moved, settling gradually into oblivion. Frank turned the flash downward and they watched in astonishment as the two-pound pebble floated deliberately down the center of the shaft at the rate of not more than one foot in each second. "Well, I'll be doggoned," breathed Frank admiringly. "Leland has done it. He has conquered gravity. For, in that pit at least, there is no gravity, or at any rate not enough to mention. It has been almost completely counteracted by some force he has discovered and now we know how to follow him down there. Come on Tommy, let's go!" And, suiting action to his words, Frank jumped into the mouth of the pit where he bobbed about for a moment as if he had jumped into a pool of water. Then slowly he sank from view, and Tommy followed him. * * * * * It was a most unique experience, that drop into the heart of the mountain. Practically weightless, the two young men found it quite difficult to negotiate the passage. For the first hundred or more feet they continued to bump about in the narrow shaft and each sustained painful bruises before he learned that the best and simplest method of accommodating himself to the strange condition was to remain absolutely motionless and allow the greatly weakened gravity to take its course. Each movement of an arm or leg was accompanied by a change in direction of movement, and contact with the hard stone walls followed. If they endeavored to push themselves from the contact the result was likely to be an even more serious bump on the opposite side of the shaft. So they continued the leisurely drop into the unknown depth of the pit. Frank had turned off the flashlamp, for its battery was giving out and he wished to conserve its remaining energy for eventualities. Thus they were in Stygian darkness for nearly a half-hour, though the green luminosity far beneath them grew stronger with each passing minute. It now revealed itself as a clearly defined disc of light that flickered and sputtered continually, frequently lighting the lower end of the shaft with an unusual burst of brilliance. Remotely distant it seemed though, and unconscionably slow in drawing nearer. "How far do you think we must drop?" called Tommy to Frank, who was probably fifty feet below him in the shaft. "Well, I figure we have fallen about a thousand feet so far," came the reply, "and my guess is that we are about one third of the way down." "Then this shaft is over a half-mile deep, you think?"