These cubes then, were indeed sentinels--sentinels impossible to injure. Though no force had been used against Sarka and Jaska, Sarka had the feeling that they were powerless, and that here on the edge of a crater of the Moon awful forces were being mustered against them. Mustered slowly, sluggishly, yet surely, as though the mentality which mustered them knew them helpless, and that there was no need to hurry! As for Jaska, she merely clung to Sarka and waited--trusting him no matter what might transpire. On a blind chance, Sarka brought out his ray director again, turned its muzzle toward that invisibly-blue column, pressed with his fingers, moving the director back and forth. Instantly the blue column seemed to break short off, while the broken upper portion started racing outward toward the Earth. Sarka watched it, and noted that the yellowish glow on the Earth, even as he watched, was fading out--disappearing! "If the ray will smash the blue column, Jaska," he said, "it will also destroy its source! Come! We will go look for it!" And, holding her hand tightly, he rose to his feet and strode boldly down the inner slope of the vast crater. CHAPTER XIV _The Crater Gnomes_ It seemed to Sarka, as he moved down the inner slope of the crater, that the cubes were somehow making sport of him, laughing at him, though no hint of laughter or anything resembling laughter emanated from them. But, shutting his lips grimly, holding fast to Jaska's hand, he proceeded on, reached the lower portion of the inner slope, where it dropped off into a seeming black abyss, and dropped, keeping to a safe speed because of the fact that both he and Jaska were attired for movement in the air--though their manner of aerial transportation could scarcely be called flying. The anti-gravitational ovoids simply rendered ineffectual the law of gravity. Down they dropped, endlessly it seemed, while all about them, growing gradually, a bluish glow began to make itself manifest. Sarka turned and looked at the face of Jaska and noted that it--all her being--was glowing with this strange radiance. He smiled at her, and she smiled back. Looking down now, to what seemed still a vast depth, they could see figures moving, tiny, almost infinitesimal, about a great circular cone, out of the depths of which came that strange bluish column whose outer tip touched the Earth. * * * * * Some inner sense warned Sarka not to touch that column, or to permit Jaska to do so. They dropped down beside it, while Sarka, for no reason that he could assign, once more took his ray director in his free hand and held it in readiness. It seemed so tiny and futile--so foolish for two people, one of them a woman--to go into the very heart of an alien world, against an unknown enemy, armed with such a tiny weapon. Two people against unguessed myriads, whose very nature was an enigma, even to Sarka.