178 The Rev. Mr. Buckland’s account of Fossil Teeth and 
casual intersection by some artificial operations, will lead to 
the knowledge of their existence ; and in this circumstance, 
we also see a reason why so few caverns of this kind have 
hitherto been discovered, although it is probable that many 
such may exist. 
In all these cases, the bones found in caverns are never 
mineralised, but simply in the state of grave bones, or incrusted 
by stalactite; and have no farther connection with the rocks 
themselves, than that arising from the accident of having 
been lodged in their cavities, at periods long subsequent to 
the formation and consolidation of the strata in which these 
cavities occur. 
On entering the cave at Kirkdale (see Plate XVI. fig. 2), 
the first thing we observe is a sediment of mud, covering 
entirely its whole bottom to the average depth of about 
a foot, and entirely covering and concealing the subjacent 
rock, or actual floor of the cavern. Not a particle of mud is 
found attached either to the sides or roof ; nor is there a trace 
of it adhering to the sides or upper portions of the transverse 
fissures, or any thing to suggest the idea that it entered 
through them. The surface of this sediment when the cave 
was first entered was nearly smooth and level, except in 
those parts where its regularity had been broken by the ac- 
cumulation of stalagmite above it, or ruffled by the dripping 
of water : its substance is argillaceous and slightly micaceous 
loam, composed of such minute particles as would easily be 
suspended in muddy water, and mixt with much calcareous 
matter, that seems to have been derived in part from the 
dripping of the roof, and in part from comminuted bones. 
Above this mud, on advancing some way into the cave, the 
