"Its structure should be clear to you, although you probably could not prepare it upon Tellus because of your high temperature. It is nothing but nitrogen--twenty-six atoms of nitrogen combined to form one molecule of what you would call--N-twenty-six?" "Wow!" Stevens whistled. "Crystalline, pentavalent nitrogen--no wonder it's violent!" "We could, of course, cover your vessel with the mirror, but I am afraid that it would prove of little value. The plates are so hot that it would soon volatilize." "Not necessarily," argued Stevens. "We could live in number one life-boat, and shut off the heat everywhere else. The life-boats are insulated from the structure proper, and the inner and outer walls of the structure are insulated from each other. With only the headquarters lifeboat warm, the outer wall could be held pretty close to zero absolute." "That is true. The bombs, of course, are controlled by radio, and therefore may be attached to the outer wall of your vessel. We shall be glad to do these small things for you." The heaters of the _Forlorn Hope_ were shut off, and as soon as the outer shell had cooled to Titanian temperature, a corps of mechanics set to work. A machine very like a concrete mixer was rolled up beside the steel vessel, and into its capacious maw were dumped boxes and barrels of dry ingredients and many cans of sparkling liquid. The resultant paste was pumped upon the steel plating in a sluggish, viscid stream, which spread out into a thick and uniform coating beneath the flying rollers of the skilled Titanian workmen. As it hardened, the paste smoothed magically into the perfect mirror which covered the space-vessels of the satellite; and a full dozen of the mirror explosive bombs of this strange people were hung in the racks already provided. "Once again I must caution you concerning those torpedoes," Barkovis warned Stevens. "If you use them all, very well, but do not try to take even one of them into any region where it is very hot, for it will explode and demolish your vessel. If you do not use them, destroy them before you descend into the hot atmosphere of Ganymede. The mirror will volatilize harmlessly at the temperature of melting mercury, but the torpedoes must be destroyed. Once more, Tellurians, we thank you for what you have done, and wish you well." "Thanks a lot for _your_ help--we still owe you something," replied Stevens. "If either of your power-plants go sour on you again, or if you need any more built, be sure to let us know--you can come close enough to the inner planets now on your own beam to talk to us on the ultra-communicator. We'll be glad to help you any way we can--and we may call on you for help again. Goodbye, Barkovis--goodbye, all Titania!"