For although the spectacular major dune formations of the Great Erg have defied wheeled vehicles since the era of the Carthaginian chariots, and even the desert born camel limits his daily travel in them to but a few miles, the modern hovercraft, atop its air cushion jets, finds them of only passing difficulty to traverse. And the hovercraft leaves no trail. Cliff Jackson scowled out at the identical scenery. Identical for more than two hundred miles. For twice that distance, they had seen no other life. No animal, no bird, not a sprig of cactus. This was the Great Erg. He muttered, "This country is so dry even the morning dew is dehydrated." Isobel laughed--she, too, had never experienced this country before. "Why, Cliff, you made a funny!" They were sitting three across in the front seat, with Homer Crawford at the wheel, and now all three were dressed in the costume of the Kel Rela tribe of the Ahaggar Tuareg confederation. In the back of the lorry were the jerry-cans of water and the supplies that meant the difference between life and mummification from sun and heat. Cliff turned suddenly to the driver. "Why here?" he said bitterly. "Why pick this for a base of operations? Why not Mopti? Ten thousand Sudanese demonstrated for El Hassan there less than two weeks ago. You'd have them in the palm of your hand." Homer didn't look up from his work at wheel, lift and acceleration levers. To achieve maximum speed over the dunes, you worked constantly at directing motion not only horizontally but vertically. He said, "And the twenty and one enemies of the El Hassan movement would have had us in their palms. Our followers in Mopti can take care of themselves. If this movement is ever going to be worth anything, the local characters are going to have to get into the act. The current big thing is not to allow El Hassan and his immediate troupe to be eliminated before full activities can get under way. For the present, we're hiding out until we can gather forces enough to free Tamanrasset." "Hiding out is right," Cliff snorted. "I have a sneaking suspicion that not only will they never find us, but we'll never find them again." Homer laughed. "As a matter of fact, we're not so far right now from Silet where there's a certain amount of water--if you dig for it--and a certain amount of the yellowish grass and woody shrubs that the bedouin depend on. With luck, we'll find the Amenokal of the Tuareg there." "Amenokal?" "Paramount chief of the Ahaggar Tuaregs." * * * * * The dunes began to fall away and with the butt of his left hand Crawford struck the acceleration lever. He could make more time now when less of his attention was drawn to the ups and downs of erg travel. Patches of thorny bush began to appear, and after a time a small herd of gazelle were flushed and high tailed their way over the horizon. Isobel said, "Who is this Amenokal you mentioned?"