Here is a little more about the French book I was describing. It is not a novel, but a geologic book. The book has lots of interesting sketches which resemble some of the scenes later used in the Jules Vernes story:
http://www.geology.19thcenturyscience.org/books/1872-Figuier-BeforeFlood/plates-200/p015.jpg There is also a sketch of a geyser in Iceland. Here is the link containing the text and photos of an English translation of the book: http://www.geology.19thcenturyscience.org/books/1872-Figuier-BeforeFlood/htm/doc.html I bet there is something in the book about caves, but I did not look. David Locklear
