Communications and mathematics and the electronic brains of calculating machines had done all that they could do; the rest was up to human skill, to the perfection of co-ordination and the speed of reaction of human mind, nerve, and muscle. Kinnison's glance darted from plate to panel to computer-tape to meter to galvanometer and back to plate; his left hand moved in tiny arcs the knobs whose rotation varied the intensities of two mutually perpendicular components of his torpedoes' drives. He listened attentively to the reports of triangulating observers, now giving him data covering his own missiles, as well as the target object. The fingers of his right hand punched almost constantly the keys of his computer; he corrected almost constantly his torpedoes' course. "Up a hair," he decided. "Left about a point." The target moved away from its predicted path. Down two--left three--down a hair--_Right_! The thing was almost through Zone Two; was blasting into Zone One. He thought for a second that his first torp was going to connect. It almost did--only a last-instant, full-powered side thrust enabled the target to evade it. Two numbers flashed white upon his plate; his actual error, exact to the foot of distance and to the degree on the clock, measured and transmitted back to his board by instruments in his torpedo. Working with instantaneous and exact data, and because the enemy had so little time in which to act, Kinnison's second projectile made a very near miss indeed. His third was a graze; so close that its proximity fuze functioned, detonating the cyclonite-packed war-head. Kinnison knew that his third went off, because the error-figures vanished, almost in the instant of their coming into being, as its detecting and transmitting instruments were destroyed. That one detonation might have been enough; but Kinnison had had one glimpse of his error--how small it was!--and had a fraction of a second of time. Hence Four and Five slammed home; dead center. Whatever that target had been, it was no longer a threat. "Kinnison, in," he reported briefly to Fire Control, and took over from Harper the direction of the activities of Sector A. The battle went on. Kinnison sent Harper and Drummond out time after time. He himself was given three more targets. The first wave of the enemy--what was left of it--passed. Sector A went into action, again at extreme range, upon the second. Its remains, too, plunged downward and onward toward the distant ground. The third wave was really tough. Not that it was actually any worse than the first two had been, but the CR10685 was no longer getting the data which her Technos ought to have to do a good job; and every man aboard her knew why. Some enemy stuff had got through, of course; and the observatories, both on the ground and above it--the eye of the whole American Defense--had suffered heavily.