The mule tottered to one of the sand patches and thrust her nose into the sand with a hoarse, rattling grunt. At the same moment it flashed across Tom's half-clouded mind that water is often found beneath the dry beds of vanished African streams. He cut his hand loose, flung himself down on the sand, and began to dig with his knife feebly but desperately. The mule, meanwhile, began scraping with her fore-hoofs, and this encouraged him to go on. He broke the sand up with the knife-blade, and scooped it out with his hands. Presently the knife-blade began to rattle and clink against pebbles in the sand, and when the hole was about a foot deep there were more stones than sand.
He thrust his hands down and brought up a double handful of them. He happened to look at them before he threw them away, and as he did so a sound something like what the mule was making came from his throat. The
