were migratory. There were any number of plausible explanations of their absence.
His preliminary scrutiny of the immediate environment satisfactorily concluded—and no motile form of Earth-life having yet appeared to inspect his ship, attempt communication with him or perhaps dispute his peaceful invasion of the planet—Thvall determined to inspect one of the buildings which towered skyward only a quarter of a mile away, to the southward. Prudently burdening himself with a variety of apparatus and weapons, which he distributed among several of his smaller tentacles, he emerged through the airlock in his ship's hull and crawled rapidly and with a slight tingling of anticipation toward the nearest of the buildings.
He had proceeded only a short distance when he came upon a bleached mass of human bones, half hidden in the rank grass. Examining them, he realized at once that they had lived, but—as his own amorphous race lacked rigid skeletal structure of any sort, and any conception of motile life being hampered by rigidity was alien to him—he had difficulty in imagining what the creature had been like in life. He concluded that it had been nowhere near as motile as himself—perhaps little more motile than the vegetation. He also noted, however, and with considerable approval, a number of fat gray earthworms, and he paused and attempted to communicate with them, quickly discovering, however, that, though they knew fear and hunger, they were incapable of abstract thought.
Continuing onward, he ascended a long ramp which debouched upon a broad street. On the opposite side of the street the buildings began. The street was littered with a large number of small, egg-shaped wheeled mechanisms. Examining one of these through its windows of fused silica and metallic oxides, Thvall saw that it contained two skeletons.
It was obvious to him now that these dead were of the species which had built the city. Why were they dead? And had all of their kind throughout the city perished? Or were some left alive?
Uneasily Thvall, who realized only too well that the unknown doom which had snuffed out this bony form of Earth-life might also be inimical to himself, paused and made additional tests. Reassurance of a sort returned to him as he determined that Earth's atmosphere was remarkably stable and chat there were no electrical or atomic mechanisms operating within the field of his apparatus. Nevertheless, he determined to proceed with extreme wariness.
Crossing the broad street, Thvall approached the base of the nearest building and examined as much of the interior as he could see through the dusty though still partly transparent windows. The structure was internally subdivided into many small cubicles profusely equipped with furnishings which were, for the most part, incomprehensible to Thvall: he would have to see those objects in use before he could understand their purpose.
His bulk was too great to permit him to enter through any of the windows, but there were large doors which, after a brief examination, he easily opened. Entering the building, he found himself in a chamber of considerable size, which, like the smaller cells, was luxuriously furnished. The walls of this room were profusely paneled with mirrors, which created the illusion of a
