extended to its utmost possible spread, upon the most carefully
plotted prolongation of the line of the torpedo's flight, only to have
the projection flash far beyond the vessel's furthest possible position
without a reaction from the far-flung screen. Then he would go back to
the torpedo, make a minute alteration in his line, and again flash
forward, only to miss it again. Finally, after thirty fruitless attempts
to bring his detector screen into contact with the nearest Fenachrone
ship, he gave up the attempt, rammed his battered, reeking briar full of
the rank blend that was his favorite smoke, and strode up and down the
floor of the projector base--his eyes unseeing, his hands jammed deep
into his pockets, his jaw thrust forward, clamped upon the stem of his
pipe, emitting dense, blue clouds of strangling vapor.

"The maestro is thinking, I perceive," remarked Dorothy, sweetly,
entering the projector from an airboat. "You must all be blind, I
guess--you no hear the bell blow, what? I've come after you--it's time
to eat!"

"'At-a-girl, Dot--never miss the eats! Thanks," and Seaton put his
problem away, with perceptible effort.

"This is going to be a job, Mart," he went back to it as soon as they
were seated in the airboat, flying toward "home." "I can nail them, with
an increasing shift in azimuth, up to about thirty thousand light-years,
but after that it gets awfully hard to get the right shift, and up
around a hundred thousand it seems to be darn near impossible--gets to
be pure guesswork. It can't be the controls, because they can hold a
point rigidly at five hundred thousand. Of course, we've got a pretty
short back-line to sight on, but the shift is more than a hundred times
as great as the possible error in backsight could account for, and
there's apparently nothing either regular or systematic about it that I
can figure out. But.... I don't know.... Space is curved in the fourth
dimension, of course.... I wonder if ... hm--m--m." He fell silent and
Crane made a rapid signal to Dorothy, who was opening her mouth to say
something. She shut it, feeling ridiculous, and nothing was said until
they had disembarked at their destination.

"Did you solve the puzzle, Dickie?"

"Don't think so--got myself in deeper than ever, I'm afraid," he
answered, then went on, thinking aloud rather than addressing any one in
particular:

"Space is curved in the fourth dimension, and fifth-order rays, with
their velocity, ma