OF THE BONES, MUD, AND PEBBLES, IN CAVES NEAR SPA. Ill 
osseous breccia, resembling that of Gibraltar, and along the shores of 
the Mediterranean, but not so red. It resembles it also in being full 
of irregular cells, and of small veins, that are lined internally with a 
thin pellicle of stalagmite. In this breccia of the under vaultings 
artificial holes, or small galleries, have been dug to extract the bones; 
and of these only it is true that the roof and sides, as well as the 
floor, have bones adhering to them : in the natural chambers there is 
not a single fragment of bone, except upon the floor. 
These general observations apply to the caves and fissures near 
Spa, as well as to those in the Hartz Forest and Franconia, and it 
will be convenient to begin my more detailed account of them with 
those cases that are most simple. 
I. CAVES NEAR SPA. 
In the transition limestone which occurs in the neighbourhood 
of Spa, at Theux, and Verviers, I found numerous vertical fissures 
extending upwards to the surface, and often communicating laterally 
with other fissures and with small caverns. All these fissures were 
filled entirely, and the caverns partially, with a mass of diluvial mud 
and rolled pebbles. Amongst the latter were chalk, flints, and many 
varieties of quartz and slate rocks. The mud in some of the larger 
fissures abounds with ochreous concretions, formed stalagmitically 
since its introduction to its present vertical position ; and like that in 
the cave near Wirkswortli, illustrates the history of the ochre I have 
before mentioned, as having been worked in a similar fissure con- 
