His first care was to tap Siblin's beam, but his call elicited no response. Those ultrainstruments were then lying neglected in a corner of an air-filled room upon far Chlora, where the almost soundless voice of the tiny receiver went unheard. Setting upon his receiver a relay alarm to inform him of any communication from Siblin, Radnor joined the force of men who were smoothly and efficiently re-equipping his vessel. In a short time the alterations were done, and, armed now to the teeth with vibratory and with solid and gaseous destruction, he lifted his warship into the air, grimly determined to take the war into the territory of the enemy. He approached the inimical planet cautiously, knowing that their cities would not be undefended, as were those of his own world, and fearing that they might have alarms and detector screens of which he could know nothing. Poised high above the outermost layer of that noxious atmosphere he studied for a long time every visible feature of the world before him. In this survey he employed an ordinary, old-fashioned telescope instead of his infinitely more powerful and maneuverable visirays, because the use of the purely optical instrument obviated the necessity of sending out forces which the Chlorans might be able to detect. He found the diamond-shaped ocean and the elliptical lake without difficulty, and placed his vessel with care. He then cut off his every betraying force and his ship plunged downward, falling freely under the influence of gravity. Directly over the city Radnor actuated his braking rockets, and as they burst into their staccato thunder his hands fairly flashed over his controls. Almost simultaneously he scattered broadcast his cargo of bombs, threw out a vast hemisphere of force to confine the gas they would release, activated his spy ray, and cut in the generators of his awful offensive beams. The bombs were simply large flasks of metal, so built as to shatter upon impact, and they contained only oxygen under pressure--but what a pressure! Five thousand Valeronian atmospheres those flasks contained. Well over seventy-five thousand pounds to the square inch in our ordinary terms, that pressure was one handled upon Earth only in high-pressure laboratories. Spreading widely to cover almost the whole circle of the city's expanse, those terrific canisters hurtled to ground and exploded with all the devastating might of the high-explosive shells which in effect they were.