"Undoubtedly, then. Grant that it is impenetrable to all matter and to all known waves. Suppose that it should prove impenetrable also to gravitation and to magnetism? Those phenomena probably depend upon the ether, but we know nothing fundamental of their nature, nor of that of the ether. Therefore your calculations, comprehensive though they are, cannot predict the effect upon them of your zone of force. Suppose that that zone actually does set up a barrier in the ether, so that it nullifies gravitation, magnetism, and all allied phenomena; so that the power-bars, the attractors and repellers, cannot work through it? Then what? As well as showing me the zone of force, you might well have shown me yourself flying off into space, unable to use your power and helpless if you released the zone. No, we must know more of the fundamentals before you try even a small-scale experiment." "Oh, bugs! You're carrying caution to extremes, Mart. What can happen? Even if gravitation should be nullified, I would rise only slowly, heading south the angle of our latitude--that's thirty-nine degrees--away from the perpendicular. I couldn't shoot off on a tangent, as some of these hot-heads have been claiming. Inertia would make me keep pace, approximately, with the earth in its rotation. I would rise slowly--only as fast as the tangent departs from the curvature of the earth's surface. I haven't figured out how fast that is, but it must be pretty slow." "Pretty slow?" Crane smiled. "Figure it out." "All right--but I'll bet it's slower than the rise of a toy balloon." Seaton threw down the papers and picked up his slide-rule, a twenty-inch trigonometrical duplex. "You'll concede that it is allowable to neglect the radial component of the orbital velocity of the earth for a first approximation, won't you--or shall I figure that in too?" "You may ignore that factor." "All right--let's see. Radius of rotation here in Washington would be cosine latitude times equatorial radius, approximately--call it thirty-two hundred miles. Angular velocity, fifteen degrees an hour. I want secant fifteen less one times thirty-two hundred. Right? Secant equals one over cosine--um-m-m-m--one point oh three five. Then point oh three five times thirty-two hundred. Hundred and twelve miles first hour. Velocity constant with respect to sun, accelerated respecting point of departure. Ouch! You win, Mart--I'd kinda step out! Well, how about this, then? I'll put on a vacuum suit and carry rations. Harness outside, with the same equipment I used in the test flights before we built _Skylark I--plus_ the new stuff and a coil. Then throw on the zone, and see what happens. There can't be any jar in taking off, and with that outfit I can get back O. K. if I go clear to Jupiter!"