The girl glanced at it thoughtfully for a moment, and, drawing toward her a pad of yellow paper, she swiftly integrated the equation before Bennie's embarrassed but admiring eyes. "I suppose one gets groggy occasionally," she said. "Of course I can see that you're on some gravitational problem." "Yes," he replied; "I'm trying to calculate the rate at which the velocity of the Flying Ring--Pax's antigravity machine that I found up in Labrador, you know--would increase as it left the earth if I took it out into space. The attraction of gravitation, at a distance, say, of twelve thousand miles above the earth would amount to comparatively little, and our velocity would increase at a simply terrific rate. I must get an absolute solution of the problem. Skooting round in space would have to be done by a sort of dead reckoning, I suppose, anyhow, but a knowledge of our velocity would be essential, wouldn't it?" "By 'our velocity' do you mean that you are planning to take me with you?" inquired the young lady pleasantly. At this highly indelicate suggestion, Professor Hooker stared at his fair companion blankly. "You--I--thunder--no!" he stammered, suddenly turning pink and experiencing a sensation of warm stickiness around his collar. "Wouldn't do at all, you know! No idea of such a thing! Hope you didn't think--" She leaned back again in her chair and rested her head against the wall, looking dreamily over Bennie's head to a great astronomical chart hanging upon the opposite side of the room. "You know," she responded, and there was almost a suggestion of awe in her voice. "I have sometimes thought of the unlimited possibilities which the Flying Ring would afford to a person who had the courage to avail himself--or herself--of them. There is nothing, so far as I can see, to prevent your navigating the Ring anywhere in space. Provided you arranged for a sufficient supply of oxygen, a flight to the moon would hardly present any difficulties at all." "Very little," answered Bennie. "It is perfectly plain that Pax had anticipated just such a flight, for the Ring is fully equipped with oxygen-tanks and all sorts of similar appliances. It may be that he actually did visit the moon! So long as I can get uranium cylinders for my tractor, I could take the Ring anywhere. But there are other considerations, certain chances that a chap oughtn't to take--unless he hopes to accomplish something worth while. The navigation of interplanetary space is an entirely new game, and the chances are that, no matter how much care I took, I shouldn't learn all the rules the first time. Then, if anything went wrong--" "If anything went wrong, and your engine ran down, or something happened to your machinery, you might find yourself caught between the gravitation of the moon and of the earth and whirling round and round forever through the universe." Bennie took a long pull on his pipe.