But it did not take long for those officers to tune in their offensive armament, and that armament was driven by no such puny engines as Radnor's space ship bore. Being stationary and a part of the regular equipment of a fortress, their size and mass were of course much greater than anything ordinarily installed in any vessel, of whatever class or tonnage. Also, in addition to being superior in size and number, the Chloran generators were considerably more efficient in the conversion and utilization of interatomic energy than were any then known to the science of Valeron. Therefore, as Radnor had rather more than expected, he was not long allowed to wreak his will. From the dome there reached out slowly, almost caressingly, a huge arm of force incredible, at whose first blighting touch his first or outer screen simply vanished--flared through the visible spectrum and went down, all in the veriest twinkling of an eye. That first screen, although the weakest by far of the four, had never even radiated under the heaviest test loads that Radnor had been able to put upon it. Now he sat at his instruments, tense but intensely analytical, watching with bated breath as that Titanic beam crashed through his second screen and tore madly at his third. * * * * * Well it was for Valeron that day that Radnor had armed and powered his vessel to withstand not only whatever forces he expected her to meet, but had, with the true scientific spirit and in so far as he was able, provided against any conceivable emergency. Thus, the first screen was, as has been said, sufficiently powerful to cope with anything the vessel was apt to encounter. Nevertheless, the power of the other defensive courses increased in geometrical progression; and, as a final precaution, the fourth screen, in the almost unthinkable contingency of its being overloaded, threw on automatically in the moment of its failure an ultimately impenetrable zone of force. That scientific caution was now to save not only Radnor's life, but also the whole civilization of Valeron. For even that mighty fourth screen, employing in its generation as it did the unimaginable sum total of the power possible of production by the massed converters of the space flyer, failed to stop that awful thrust. It halted it for a few minutes, in a blazingly, flamingly pyrotechnic display of incandescence indescribable, but as the Chlorans meshed in additional units of their stupendous power plant it began to radiate higher and higher into the ultra-violet and was certainly doomed.