"How does that help matters?" asked Crane in wonder. "Of course it is not surprising that no lines of force were visible, but I thought that your detectors screens would have found them if any such guiding beams had been present."
"The ordinary bands, if of sufficient power, yes. But there are many possible tracer rays not reactive to a screen such as I was using. It was very light and weak, designed for terrific velocity and for instantaneous automatic arrest when in contact with the enormous forces of a power bar. It wouldn't react at all to the minute energy of the kind of beams they'd be most likely to use for that work. Caslor's certainly right. They're steering their torpedoes with tracer rays of almost infinitesimal power, amplified in the torpedoes themselves—that's the way I'd do it myself. It may take a little while to rig up the apparatus, but we'll get it—and then we'll run those birds ragged—so fast that their ankles'll catch fire—and won't need the fourth-dimensional correction after all."
When the bell announced the beginning of the following period of labor, Seaton and his co-workers were in the Area of Experiment waiting, and the work was soon under way.
"How are you going about this, Dick?" asked Crane.
"Going to examine the nose of one of those torpedoes first, and see what it actually works on. Then build me a tracer detector that'll pick it up at high velocity. Beats the band, doesn't it, that neither Rovol nor I, who should have thought of it first, ever did see anything as plain as that? That those things are following a ray?"
"That is easily explained, and is no more than natural. Both of you were not only devoting all your thoughts to the curvature of space, but were also too close to the problem—like the man in the woods, who cannot see the forest because of the trees."
"Yeah, may be something in that, too. Plain enough, when Caslor showed it to us," said Seaton.
While he was talking, Seaton had projected himself into the torpedo he had lined up so many times the previous day. With the automatic motions set to hold him stationary in the tiny instrument compartment of the craft, now traveling at a velocity many times that of light, he set to work. A glance located the detector mechanism, a set of short-wave coils and amplifiers, and a brief study made plain to him the principles underlying the directional loop finders and the controls which guided the flying shell along the path of the tracer ray. He then built a detector structure of pure force immediately in front of the torpedo, and varied the frequency of his own apparatus until a meter upon one of the panels before his eyes informed him that his detector was in perfect resonance with the frequency of the tracer ray. He then moved ahead of the torpedo, along the guiding ray.
"Guiding it, eh?" Dunark congratulated him.