“Never,” the lad replied.
“I thought not,” commented the leader of the expedition, “or you wouldn’t talk so glibly about doing it over a camel’s wobbly hump. You’ve got to have something solid, like a mule’s ribs, if you want to tighten cinches to that extent.”
“I suppose the Arabs know best, at that,” the boy admitted. “After all, these Egyptian chaps have been loading camels for a good many thousand years.”
“Exactly. And besides, Perry, this climb is unusual traveling for camels. They’re accustomed to the level or to the slopes of sand dunes. Except for the Egyptian Survey, which discovered this bone deposit a few years ago, probably no one has taken the trouble to climb this cliff since the days that Lake Moeris occupied a large part of the valley below.”
On the next tier above, Perry suddenly found a vast change in the character of the rock and saw thousands of beautiful sea-shells in the solid limestone scattered on every side.
Off his camel he jumped again, and filled his pockets with bits of stone containing the shells. They were heavy to carry in the intense heat, when every extra ounce counted, but he simply could not pass them by.
“This must have been the bed of the sea for a long time,” said the lad to Antoine, “this limestone deposit is so thick.”
“Yes, yes,” his friend answered. “The Mediterranean came down south of this. Of course, the shore has changed many times.”
“What has built up all the north coast of Africa,” queried Perry, “just the rising of the land?”
“Partly; but a great deal of it was caused by the discharge of the mud of rivers and streams, making new land, in the same way that the Mississippi is making new land in the Gulf of Mexico. But you see, Perry, as fast as the new land was made, the continent sank, so that the filling and sinking went ahead at about the same rate. Sometimes the sea won out, and we find a layer that is marine; sometimes the land won out, and the layer is a river or fresh-water deposit. When we start to dig out fossils, you’ll probably find land and sea creatures close together. That’s because when it was a shallow sea, the marine creatures died and their bones sank to the bottom, and when it was marsh, the land animals died in the swamp and the bones became covered with mud. Then the sea took the upper hand again, as the continent sank.”