That deep, throbbing noise frightened Dan as none of his previous experiences had done. Shivering from fear as much as from cold, he crouched down beside a huge boulder in the edge of the tangle of brush that covered the bottom of the ravine. His heart pounded wildly. He was in the clutches of an unreasoning fear that some terrible Thing had seen him, and was about to seek him out. For a moment he had to use all his will to keep himself from panic flight through the brush. The unknown is always terrible, and he had invaded the domain of a force he could not understand.
In a moment, however, he recovered himself. He would be as safe there in the jungle, he thought, as anywhere on the island. He thought of starting a fire, then realized that he had no matches, and that he would not dare to make a light if he were able. He pulled a few handfuls of dry grass to make a sort of bed, upon which he huddled up, thanking his lucky stars that the island was in semi-tropical latitudes.
His mind returned again to the riddles that confronted him: the green flash and the strange mechanism on the peak. He recalled fantastic stories he had read, of hermit scientists conducting amazing experiments in isolated parts of the world. Presently he decided that something of the kind must be on foot here.
"The green flash is a sort of a death ray," he summed up, aloud. "And they shoot it from that bright needle. No wonder they don't want to be bothered! Somebody may be fixing to upset civilization!
"But it's queer that the needle points at Mars...."
Of this last fact, which might have been a clue to the most reasonable solution of the mystery, if a rather astounding one, he was able to make nothing. In fact, huddled up on his pile of grass in some degree of comfort, he presently went to sleep, still pondering in vain upon this last clue.
e was awakened by a soft, insistent purring sound, rather like that of a small electric motor run without load at very high speed. Recollection of the night's events came abruptly to him, and he sprang to his feet in alarm, finding his muscles sore and stiff from his cramped position.
From one side Dan heard the rumble of thunder, and, glancing up, saw that the sky above the sea was overcast with a rolling mass of dark, menacing clouds. There was a strange portentous blackness about these storm clouds that filled him with a nameless fear.