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of stalactite, more or less resembling tables, altars, organs, and 
other objects, named according to tbe taste of guides, rather 
than from any real or traceable resemblance. 
In such limestone caverns, the smallest chambers, and often 
very minute subdivisions of them, are characterized by these 
curious accumulations quite as much as the great halls. Com- 
mencing with the lifting up of the limestone mass in its hardened 
state, the cracking of the surface, and the first infiltration of 
rain-water, the construction of ordinary stalactites and stalag- 
mites in caverns has gone on unchecked, being guided onl) T by 
the accidental course of the fissures and crevices. But there is 
another kind of deposit within these limestone vaults which is also 
interesting, and on which much depends. It is the flat floor that 
is commonly noticeable, especially in the chambers near the out- 
let, and that is independent, to some extent, of the stalagmitic 
base of columns. This floor is composed partly of an impalpable 
mud containing non ochre, and has been derived from foreign 
material carried in by the water from above, or drifted in from 
some side entrance. From time to time, a coating of stalagmite, 
nearly horizontal, has formed on the surface of the mud, sepa- 
rating the floors of different periods of the cavern's history, and 
enabling us to judge of the comparative date of any foreign 
objects found buried. Many such coats succeed each other at 
intervals, and fragments of old stalactite and stalagmite are often 
confusedly mixed up with the mud of the floor, and re-cemented. 
This brings us to the second part of the history of caverns, 
which we must reserve for another chapter. It will there be 
shown that, connected with the mechanical facts we have been 
describing, there is associated a group of natural-history facts 
of the most singular kind, pointing to conclusions with reference 
to organic life, and even to the history of the human race, not 
surpassed in interest and importance by any department of 
geological investigation. 
