"What make de cave, anyhow?" asked Cudjo.
"The wery question I vas going to ask," said Carl.
"It will take but a few words to tell you all I know about it," said Penn. "Water containing carbonic acid gas has the quality of dissolving such rock as this part of the mountain is made of. It is limestone; and the water, working its way through it, dissolves it as it would sugar, only very slowly. Do you understand?"
"O, yes, massa! de carbunkum asses tote it away!"
Penn smiled, and continued his explanation, addressing himself to Carl.
"So, little by little, the interior of the rock is worn, until these great cavities are formed."
"But what comes o' de rock?" cried Cudjo; "dat's de question!"
"What becomes of the sugar that dissolves in your coffee?"
"Soaks up, I reckon; so ye can't see it widout it settles."
"Just so with the limestone, Cudjo. It soaks up, as you say. And see!—I will show you where a little of it has settled. Notice this long white spear hanging from the roof."