They started off, and then Alan noticed a curious thing. She walked as though weighted to the ground by some invisible load. She did not raise her feet normally, but dragged them, like a diver who walks on land in his heavily weighted iron shoes. After a few steps she spread her wings, and, flapping them slowly, was able to get along better, although it was obvious that she could not lift her body off the ground to fly. For a moment Alan was puzzled, then he understood. The force of gravity on earth was too great for the power of her muscles, which were developed only to meet the pull of Mercury--a very much smaller planet. The girl was so exceedingly frail Alan judged she did not weigh, here on earth, much over a hundred pounds. But even that he could see was too much for her. She could not fly, and it was only by the aid of her wings that she was able to walk with anything like his own freedom of movement. He made her understand, somehow, that he comprehended her plight. Then, after a time, he put his left arm about her waist. She spread the great red wings out behind him, the right one passing over his shoulder; and in this fashion they went forward more easily. The girl kept constantly talking and gesturing. She seemed remarkably intelligent; and even then, at the very beginning of their acquaintanceship, she made Alan understand that she intended to learn his language. Indeed, she seemed concerned about little else; and she went about her task systematically and with an ability that amazed him. As they walked forward she kept continually stooping to touch objects on the ground--a stick, a handful of sand, a woodland flower, or a palmetto leaf. Or, again, she would indicate articles of his clothing, or his features. In each case Alan gave her the English word; and in each case she repeated it after him. Once she stopped stock still, and with astonishing rapidity and accuracy rattled off the whole list--some fifteen or twenty words altogether--pointing out each object as she enunciated the word. Alan understood then--and he found out afterward it was the case--that the girl's memory was extraordinarily retentive, far more retentive than is the case with any normal earth person. He discovered also, a little later, that her intuitive sense was highly developed. She seemed, in many instances, to divine his meaning, quite apart from his words or the gestures--which often were unintelligible to her--with which he accompanied them. After a time they reached the Mercutian vehicle. It was a cubical box, with a pyramid-shaped top, some thirty feet square at the base, and evidently constructed of metal, a gleaming white nearer like silver than anything else Alan could think of. He saw that it had a door on the side facing him, and several little slitlike windows, covered by a thick, transparent substance which might have been glass.