point on his machine, sent out a message which was read as quickly as it
was received by Van Emmon's agent, and as unconsciously translated:

"Number Eight Hundred Four, you are wanted on Plot Seventeen."

Whereupon Van Emmon's unknown assistant replied at once:

"Very well, Superior."

It was done by means of an extremely faint humming device, reminding the
geologist of certain wireless apparata he had heard. Not a word was
actually spoken by either Sanusian.

Van Emmon kept a close watch upon the conning tower on the other
machine. The sun was shining upon it in such a fashion that its gleam
made inspection very difficult. Once he fancied that he could make out a
short, compact figure within the "eye"; but he could not be sure. The
glass, or whatever it was, reflected everything within range.

Was the airman a quadruped? Did he sit or stand upright, like a man? Or
did he use all four limbs, animal-fashion? Van Emmon had to admit that
he could not tell; no wonder he didn't guess the truth.

Shortly after receiving the summons, the geologist's agent changed his
direction slightly; and within ten minutes the machine was passing over
a large grain field. On the far edge was a row of trees, and it was
toward this that the Sanusian proceeded to volplane, presently coming to
another nausea-producing stop. Once more Van Emmon was temporarily
helpless.