It was a noise like distant rumbling thunder, or the whir of some great English mill or factory; and at its sound every woman on the island threw herself on the ground prostrate, with her face in the dust, and waited there reverently till the audible voice of the god had once more subsided.

For no woman knew how that sound was produced.

Only the grown men, initiated into the mysteries of the shrine when they came of age at the tattooing ceremony, were aware that the strange, buzzing, whirring noise was nothing more or less than the cry of the bull-roarer.
A bull-roarer, as many English schoolboys know, is merely a piece of oblong wood, pointed at either end, and fastened by a leather thong at one corner.

But when whirled round the head by practised priestly hands, it produces a low rumbling noise like the wheels of a distant carriage, growing gradually louder and clearer, from moment to moment, till at last it waxes itself into a frightful din, or bursts into perfect peals of imitation thunder.

Then it decreases again once more, as gradually as it rose, becoming fainter and ever fainter, like thunder as it recedes, till the horrible bellowing, as of supernatural bulls, dies away in the end, by slow degrees, into low and soft and imperceptible murmurs.
But when the savage hears the distant humming of the bull-roarer, at whatever distance, he knows that the mysteries of his god are in full swing, and he hurries forward in haste, leaving his work or his pleasure, and running, naked as he stands, to take his share in the worship, lest the anger of heaven should burst forth in devouring flames to consume him.