“Rains, of course,” replied Frank. “During the wet season, which is due to begin up there before long, now, the Amazon sometimes rises from twenty to forty feet. Well, it is these inundations that make Cloud island valuable.”
“Like the valley of the Nile,” Alex hinted.
“Not at all in that way! It is believed that Cloud island was once an active volcano. Its top lifts above the river, at low water, about thirty feet. The summit is not more than ten acres in extent, and is as level as this deck, except that it tips gradually to the north.”
“Just a mountain tableland?” asked Alex.
“Yes, and not a very high one at that. But what makes the upper level so peculiar is that in the center there is a great crater, which sends out smoke and steam which at times hide the land. Hence the name Cloud island.”
“Why, of course!” Jule interrupted. “That is a volcanic region. But I have never heard of any Cloud island volcano!”
“It isn’t a volcano,” Frank went on. “There is never any eruption, never has been one since the records of that region were opened. Deep down in the crater are monster caverns, from which lava was tossed years ago, and at the bottom of some of these are crevices through which the steam seeps.”
“I’ll get a Russian bath when I get there!” Alex promised himself.
“You’ll get the hide scalded off you, if you go down there!” Jule advised. “Won’t he, Frank?”
“He will unless he knows where to go,” was the reply. “The steam guards well the secret of those caverns.