1822.) Bones discovered in a Cave at Kirkdale, in Yorkshire. 137 
The fact already mentioned of the engulphment of the Rical 
Beck, and other adjacent rivers, as they cross the limestone, 
showing it to abound with many similar cavities to those at 
Kirkdale, renders it likely that hereafter similar deposits of bones 
may be discovered in this same neighbourhood ; but accident 
alone can lead to such discovery, as it is probable the mouths of 
these caverns are buried under diluvian sand and gravel, or post- 
diluvian detritus ; so that nothing but their 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 mine- 
ralised, but simply in the state of grave bones, or incrusted by 
stalactite; and have no further connection with the rocks them- 
selves 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 Pl. XIV. 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 regula- 
rity had been broken by the accumulation of stalagmite above 
it, or rufiled by the dripping of water: its substance is argilla- 
ceous and slightly micaceous loam, composed of such minute 
particles as would easily be suspended im muddy water, and 
mixed 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 
roof and sides are seen to be partially studded and cased over 
with a coating of stalactite, which is most abundant in those 
parts where the transverse fissures occur, but in small quantity 
where the rock is compact and devoid of fissures. Thus far it 
resembles the stalactite of ordinary caverns; but on tracing it 
downwards to the surface of the mud, it was there found to turn 
off at right angles from the sides of the cave, and form above 
the mud a plate or crust, shooting across like ice on the surface 
of water, orcream on a panof milk. (See Pl. XIV. fig. 2.) The 
thickness and quantity of this crust varied with that found on 
the roof and sides, beg most abundant, and covering the mud 
entirely where there was much statactite on the sides, and more 
scanty in those places where the roof presented but little : in 
