While thinking over the problem he remembered that during his illness he had been entertained by the katikiro with a long story of a malignant spirit inhabiting a certain mountain some six hours' march to the south-east of the village. As a boy the katikiro could remember this terrible being bursting forth in a large sheet of flame from the bowels of the mountain, with a horrible rumbling sound that shook the solid earth for miles around, casting immense rocks miles up into the air, engulfing the surrounding country in a cloud of smoke and fire, and turning the streams into rivers of boiling mud. Many villages with all their inhabitants had been utterly destroyed; even in Barega's the shower of cinders from the sky set fire to several of the huts. For years afterwards the mountain gave off dense clouds of smoke; but these gradually ceased, and the evil spirit had since then been quiet. Nevertheless nobody from Barega's or any of the neighbouring villages had ventured to approach the mountain since these fearful happenings.
Remembering this, Tom guessed that the scene of this eruption, which was apparently an isolated peak, was connected with the great Central African volcanic system extending from Lake Kivu to the Semliki. On his march from Lake Mazingo on the track of his uncle's expedition he had passed over ground that was evidently of volcanic origin; and he surmised that this part of Central Africa had at some time or other been the scene of enormous volcanic activities. The important fact now, however, was that a volcano known to have been active was in his immediate neighbourhood. He knew that sulphurous fumes were thrown off from volcanoes; was there any chance of finding sulphur itself in any workable form on the slope of this adjacent mountain? It was worth trying, and he resolved to make a careful examination of the ground.
Next day, then, accompanied by Mbutu, half a dozen hunters to procure game, and twenty steady Bairo armed with picks and shovels, he set out with this object. He had some difficulty at first in overcoming the superstitious fears of his followers. Mbutu interpreted their objections, which, recited by their spokesman in fear and trembling and much grovelling on the earth, were quite unintelligible to Tom.