They stood in a small chamber that had walls of roughly smoothed rock. It was evidently the work of men, for tool marks showed here and there. It was lighted by a green globe set in one wall. The globe appeared to be made of some kind of flexible glass, and it glowed with a faint greenish radiance that overcame the darkness enough to give the place a dim and eerie light. At one side of the room was an oval hole like a slanting well cut in the floor. Beside it stood a pile of low, flat carts. They were about two feet wide by four feet long, and they were supported on axles bearing small wheels the diameter of a man's hand. The girl spoke to Larry twice, first in the clicking talk of the Insect-men and then in some soft and musical tongue that was unlike anything Larry had ever heard. Both times he shook his head. Motioning for them to follow her, she put one of the low carts down near the rim of the hole and sat on it. Then she gave a push with her hands--and vanished. "Come on," Larry said, raking another of the carts. Colton stared at him. "Down that hole?" he asked. "Why not? We've got to find out what all this is about." * * * * * A second later Larry Gibson found himself shooting down into the interior of the Moon by means of a sloping tunnel cut in the rock. A series of the greenish globes were set in the ceiling at intervals to give the rocky shaft a dim light. The wheels of the cart ran in two grooves cut in the floor, and he shot swiftly downward with a dull humming sound. Larry was trying to estimate the speed of his downward movement. It was not so terribly fast, probably not really as fast as the nearness of the walls made it appear while they flashed by on either hand. The slope was a gentle one. Although he had gathered considerable momentum, he had no feeling of the car being out of control. As the minutes passed, Larry saw something else. The moisture that had been on the outside of his space suit from the air within the _Sky Maid_ had frozen into a white frost a few seconds after the breaking of the control room wall let the outer cold into the ship. Now the frost was melting! They were getting into warmer regions as they went down. Perhaps they were also running into a heavier atmosphere! Larry held his hand up before him, and had a distinct feeling of pressure against it from the rush of air sweeping up to meet him. A minute later he had tested the atmosphere with the portable oxygen-gauge carried in the equipment pocket of any space suit. Then he took off his helmet. The air was quite warm, and though still very thin it was definitely breathable. Its clean, earthy odor was a pleasant contrast to the chemical product used over and over again inside the helmet of a space suit. A moment later he saw a brighter light ahead and realized that he had come to the bottom of the long shaft.