He stopped, one hand upraised in mighty emphasis, and a sudden and startling change came over him.  Downright fear drove the anger from his face; his massive body suddenly relaxed, and all his power and vigor seemed to crumble and wilt.  His hands shook; his mouth trembled.  At the same time the two women shrank from him, each giving an inarticulate cry of alarm and distress.  Dulnop gave no sound, but the anger which had left the herdsman seemed to have come to him; the youngster’s eyes flared and his breast heaved.  His gaze was fixed upon Corrus’s neck, where the sweat of fear already glistened.

Suddenly the big man dropped his head, as though in surrender.  He gasped and found voice; this time a voice as shaky and docile as it had been strong and dominant a moment before.

“Very well,” he spoke abjectly.  “Very well.  I—­shall do as you wish.”  He seemed to be talking to thin air.  “We—­will go home at once.”

And instantly all four turned about, and in perfect silence took the back trail.

III

WORLD OF MAMMOTHS

Immediately upon going into tele-consciousness Smith became aware of a decided change in his surroundings.  The interior of the study had been darkened with drawn shades; now he was using eyes that were exposed to the most intense sunlight.  The first sight that he got, in fact, was directed toward the sky; and he noted with an engineer’s keen interest that the color of the sky was blue, slightly tinged with orange.  This, he knew, meant that the atmosphere of Sanus contained at least one chemical element which is lacking on the earth.

For a minute or two the sky remained entirely clear.  There were no clouds whatever; neither did any form of winged life make its appearance.  So Smith took note of sounds.

Presumably his agent—­whoever or whatever it might be—­was located in some sort of aircraft; for an extremely loud and steady buzzing, suggesting a powerful engine, filled the engineer’s borrowed ears.  Try as he might, however, he could not identify the sound exactly.  It was more like an engine than anything else, except that the separate sounds which comprised the buzz occurred infinitely close together.  Smith concluded that the machine was some highly developed rotary affair, working at perhaps six or eight thousand revolutions a minute—­three or four times as fast as an ordinary engine.

Meanwhile his agent continued to stare into the sky.  Shortly something arrived in the field of vision; a blurred speck, far to one side.  It approached leisurely, with the unknown agent watching steadfastly.  It still remained blurred, however; for a long time the engineer knew as little about its actual form as he knew about his mysterious agent.

Then, like a flash, the vision cleared.  All the blurring disappeared instantly, and the form of a buzzard was disclosed.  It was almost directly overhead, about a quarter of a mile distant, and soaring in a wide spiral.  No sound whatever came from it.  Smith’s agent made no move of any kind, but continued to watch.