The sole apparent change in the building had occurred above the one hollow concrete pile, which seemed to indicate that if access were to be had to the mysterious, and so far only assumed spring, it must be through that pile. While the vault retained its abnormal elevation, Arthur believed that there was still water at an immense and incalculable pressure in the pipe. He dared not attempt to tap the pipe until the pressure had abated. At the end of a week he found the vault slowly settling back into place. When its return to the normal was complete he dared begin boring a hole to reach the hollow tube in the concrete pile. As he suspected, he found water in the pile--water whose sulfurous and mineral nature confirmed his belief that a geyser reaching deep into the bosom of the earth, as well as far back in the realms of time, was at the bottom of the extraordinary jaunt of the tower. Geysers were still far from satisfactory things to explain. There are many of their vagaries which we cannot understand at all. We do know a few things which affect them, and one thing is that "soaping" them will stimulate their flow in an extraordinary manner. Arthur proposed to "soap" this mysterious geyser when the renewal of its flow should lift the runaway sky-scraper back to the epoch from which the failure of the flow had caused it to fall. He made his preparations with great care. He confidently expected his plan to work, and to see the sky-scraper once more towering over mid-town New York as was its wont, but he did not allow the fishermen and hunters to relax their efforts on that account. They labored as before, while deep down in the sub-basement of the colossal building Arthur and his volunteers toiled mightily. They had to bore through the concrete pile until they reached the hollow within it. Then, when the evidence gained from the water in the pipe had confirmed his surmises, they had to prepare their "charge" of soapy liquids by which the geyser was to be stirred to renewed activity. Great quantities of the soap used by the scrubwomen in scrubbing down the floors was boiled with water until a sirupy mess was evolved. Means had then to be provided by which this could be quickly introduced into the hollow pile, the hole then closed, and then braced to withstand a pressure unparalleled in hydraulic science. Arthur believed that from the hollow pile the soapy liquid would find its way to the geyser proper, where it would take effect in stimulating the lessened flow to its former proportions. When that took place he believed that the building would return as swiftly and as surely as it had left them to normal, modern times. The telephone rang in his office, and Estelle answered it. Arthur was on the wire. A signal was being hung out for all the castaway to return to the building from their several occupations. They were about to soap the geyser.