"That product is used in the arts, but it costs too much to transport it from the places where it is found in its natural state, as science has found a much cheaper way of producing it from limestone."
"Are all these rocks limestone?"
"Beyond question. Only a few of the caves so far found are in any other formation than limestone."
"What kind of cave are those?"
"Where they have been produced by volcanic action. There the walls are of volcanic rock."
"Why is it that these underground channels are formed in this way?"
"They are formed by the erosive action of the water wearing out the softer portions of the rock beneath a harder roof or wall. This action is brought about by carbonic acid acting on the rock and producing what is called carbonate of lime, and the stalactites and stalagmites found in all these caverns are of that material."
"What is the difference between the two names you have just mentioned?"
"Stalactite means trickling or dropping, and as applied to these formations it means conical or cylindrical accretions of the carbonate. Stalagmite is the term used to designate the calcareous formations found on the floors of caverns, which are usually the droppings from the roof."
"Where are most of the caves found?"