had set everyone's temper more or less on edge and Healy flared up.
"What's the idea? Playing tag?"
Harvey pointed to the ground a few feet ahead of them and replied in one word:
"Sumidero."
Stone could see nothing but the flaky burned surface of the flat. Healy and Lefty looked about for some sign of snakes. Diamond Dick never talked much when on the march. There he appeared to conserve the slightest of efforts, reserving his talk for the evening camp. Now he stepped off and came back with a fragment of lava from a black and bristling flow that had finned its way up through the alkali. He tossed it into the air and it came down to strike the cracked surface with a sucking, suggestive plomph! In the glaring alkali appeared a splotch of black muck that geysered up as the rock sank down into a mud-pit, a masked well, too thick to flow, too liquid to dry up, a trap some ten feet in diameter, a shaft of slime perhaps twenty-five, perhaps a hundred, feet deep.
Healy shuddered. Lefty looked at the gradually disappearing patch of mud fast caking again under the fierce sun.
"Wot-o!" said the Cockney, softly. "Wot-o! Nice little prize-package that, I don't think."
"How do you tell those things? "Stone asked. "I can't tell it even now from the rest of the place."
Harvey shrugged his shoulders.
"I couldn't teach you," he said. "Can't allus tell
