"No, sir. He is out in the space ship, making another test flight. He is merely circling the world, however, so that I can easily get him on the plate here if you wish." "That would perhaps be desirable. Something very peculiar has occurred, concerning which all three of you should be informed." The connections were soon made and the Bardyle went on: "A semicircular dome of force has been erected over the ruins of the ancient city of Mocelyn. It is impossible to say how long it has been in place, since you know the ruins lie in an entirely unpopulated area. It is, however, of an unknown composition and pattern, being opaque to vision and to our visibeams. It is also apparently impervious to matter. Since this phenomenon seems to lie in your province I would suggest that you three men investigate it and take such steps as you deem necessary." "It is noted, O Bardyle," and Klynor Siblin cut the beam. He then shot out their heaviest visiray beam, poising its viewpoint directly over what, in the days before the cataclysm, had been the populous city of Mocelyn. Straight down the beam drove, upon the huge hemisphere of greenly glinting force; urged downward by the full power of the Quedrins' mighty generators. By the very vehemence of its thrust it tore through the barrier, but only for an instant. The watchers had time to perceive only fleetingly a greenish-yellow haze of light, but before any details could be grasped their beam was snapped--the automatically reacting screens had called for and had received enough additional power to neutralize the invading beam. Then, to the amazement of the three physicists, a beam of visible energy thrust itself from the green barrier and began to feel its way along their own invisible visiray. Siblin cut off his power instantly and leaped toward the door. "Whoever they are, they know something!" he shouted as he ran. "Don't want them to find this laboratory, so I'll set up a diversion with a rocket plane. If you watch at all, Vornel, do it from a distance and with a spy ray, not a carrier beam. I'll get in touch with Radnor on the way." Even though he swung around in a wide circle, to approach the strange stronghold at a wide angle to his former line, such was the power of the plane that Siblin reached his destination in little more than an hour. Keying Radnor's visibeam to the visiplates of the plane, so that the distant scientist could see everything that happened, Siblin again drove a heavy beam into the unyielding pattern of green force. [Illustration: _Surrounded by a shell of energy, he was drawn toward the huge dome._]