Suddenly, almost imperceptably, the sigma curve gave signs of flattening out. Cloud’s mind pounced. Simultaneous differential equations; nine of them. A quadruple integration in four dimensions. No matter—Cloud did not solve problems laboriously, one operation at a time. Without knowing how he had arrived at it, he knew the answer; just as the Posenian or the Rigellian can perceive every separate component particle of an opaque, three-dimensional solid, but without being able to explain to any Tellurian how his sense of perception works. It just is, that’s all.

By virtue of whatever sense or ability it is which makes a mathematical prodigy what he is, Cloud knew that in exactly seven and three-tenths seconds from that observed instant the activity of the vortex would match precisely the rating of his heaviest bomb. Another flick of his mental switch and he knew exactly the velocity he would require. His hand swept over the studs, his right foot tramped down hard upon the firing pedal; and, even as the quivering flitter rammed forward under five Tellurian gravities of acceleration, he knew to the thousandth of a second how long he would have to hold that acceleration to attain that velocity. While not really long—in seconds—it was much too long for comfort. It would take him much closer to the vortex than he wanted to be; in fact, it would take him almost to the crater’s rim.

But he stuck to the calculated course, and at the precisely correct instant he released his largest bomb and cut his dive. Then, in a continuation of the same motion, his hand slashed down through the beam of light whose cutting would activate the Bergenholm and make the vessel inertialess—safe from any form whatever of physical violence. For an instant nothing happened, and for that instant Cloud sat appalled. Neutralization of inertia took time! Not that he had ever been told that it was instantaneous—he had just assumed so. He had never noticed any time-lapse before, but now it seemed to be taking forever!

After that one instant of shocked inaction he went into ultra-speed action; kicking in the little vessel’s all-out eight-G drive and whirling her around as only a flitter or a speedster can whirl; only to see in his plate the vortex opening up like a bell-flower, or like a sun going nova.

Cloud’s forebodings were more than materialized then, for it was not only the bomb that was going off. The staggeringly immense energy of the vortex was merging with that of the detonating duodec to form an utterly indescribable explosion.

In part the flood of incandescent lava in the pit was beaten downward by the sheer, stupendous force of the blow; in part it was hurled abroad in masses, gouts, and streamers. And the raging blast of the explosion’s front seized the fragments and tore and worried them to bits, hurling them still faster along their paths of violence. And air, so densely compressed as to act like a solid, smote the walls of the crater. Those walls crumbled, crushed outward through the hard-packed ground, broke up into jaggedly irregular blocks which hurtled screamingly in all directions.

The blast-wave or explosion front buffeted the flyer while she was still partially inert and while Cloud was almost blacked out and physically helpless from the frightful linear and angular accelerations. The impact broke his left arm and his right leg; the only parts of his body not pressure-packed. Then, milliseconds later, the debris began to arrive.

Chunks of solid or semi-molten rock slammed against the hull, knocking off wings and control-surfaces. Gobs of viscous slag slapped it liquidly, freezing into and clogging up jets and orifices. The little ship was knocked hither and thither by forces she could no more resist than can a floating leaf resist a cataract; Cloud’s brain was addled as an egg by the vicious concussions which were hitting him so nearly simultaneously from so many different directions.

The concussions and the sluggings lightened . . . stopped . . . a vast peace descended, blanket-wise. The flitter was free—was riding effortlessly away on the outermost, most tenuous fringes of the storm!

Cloud wanted to faint, then, but he didn’t—quite. With one arm and leg and what few cells of his brain were still in working order, he was still in the fight. It did not even occur to him, until long afterward, that he was not going to make any effort whatever to avoid death.