Out of the spell of silence there grew presently other voices, soft whisperings, deep sighings; mysterious sounds telling of things stealthy and oppressed by the stillness; abrupt splashings that startled by their suddenness:  grunts, rumblings, and the roar of bull crocodiles.  It must not, however, be supposed that there was a continuous succession of sounds.  Each noise had its own place, and there would be often long intervals between one sound and another.

Venning, who had the first watch, found this out.  He would hear a startling splash, followed by a snort and the snap of jaws; then all would be quiet for several minutes, when, from another direction, would come perhaps a heavy sigh; then another interval of silence, again a splash, and so on until the impression grew on him that the beasts and reptiles who made the noises were working slowly towards him in a circle.

It was his first night on guard in the wilderness, and he felt the uneasiness of the hunter who discovers how limited are his senses compared with those of the wild creatures about him.  Man, himself the most secret, the most cunning, the most deadly, and, if truth must be told, the most bloodthirsty, for he kills too often for the love of killing, is the most helpless in the dark.  His sense of hearing, of sight, and of smell, fail him—­thanks to a wise provision of Nature in the interests of her other children—­for if man had the eyes of a cat, the nose of a wolf, and the hearing of a deer, he would have cleared the earth of its creatures, who would have had no rest night or day.

All the time, too, the river talked, as it rolled its great flood along, sending up a soft volume of song from the innumerable sounds produced as it washed along the islands and foamed against the rocks of the shores.  Presently, down the narrow channel, there came a rush of water which rocked the boat, and next Venning heard close at hand a strange noise, which he took to be made by a large animal cropping at the river-grass.  He looked about for a weapon, and, picking up the long boat-hook, lashed his hunting-knife to the iron hook at the top, converting it into a lance.  He had read of hippos swamping boats by seizing the narrow bows or keel in their vast jaws, and he wished to be prepared for a possible attack.  Presently the boat again rocked as another animal took to the water, then the new-comer dislodged the other with a snap of the jaws, and the first, with a complaining grunt, surged down the channel.  Venning could see nothing in the inky blackness, but he knew the beast had seen the Okapi from the short note of alarm it sounded.  Immediately the alarm was repeated.  Snorts and splashes arose from all sides.  Some great beast who had been standing unnoticed within a few yards of the boat, crashed through the bushes into the water with an uproar that woke the sleepers.

“What is it?” cried Compton.

Mr. Hume made a dart for his rifle.