k 



PREVIOUS TO THE LAST GEOLOGICAL REVOLUTION. 51 



lour and osseous structure which they display when broken, 

 have their cells lined, or sometimes quite tilledj with a stony 

 substancej and their weight is consequently so much increased 

 that they appear to be of the same specific gravity as lime- 

 stone. There is yet a third condition, in which these bones 

 depart still farther from their original character than in the 

 two above named ; that is, where the organic structure has 

 entirely disappeared, and calcareous spar is substituted for the 

 osseous substance. This alteration, I have satisfied myself, 

 is owing to the bones having lain long under water. 



It will next be my object to point out the mechanical 

 changes which these fossils have undergone, and which may 

 be treated of under three classes. First ; splits and frac- 

 tures in all directions, but for the most part longitudinal, 

 and not unfrequently accompanied by a more or less evident 

 compression of the bone. In these cases the interior surface 

 of the medullary cavity and of the cellular structure, as well 

 as the sides of the fracture, are of the same reddish yellow 

 colour as the exterior : and if the soil be impregnated with 

 calcareous particles, then are these internal surfaces overlaid 

 with a thin coating of very fine crystals of calcareous spar ; 

 but they are never filled with earth. Besides, the outer sur- 

 face being perfectly uninjured, it is ^lear that these bones 

 have been buried in the soil in a more or less fresh condition, 

 and that it was only from their increasing brittleness, that in 

 the course of time they have begun to yield to the continual 

 superincumbent pressure. To this class also belong those 

 injuries of which I have spoken in describing the cave of 

 Maquine. The bones, in that case, were not only split in all 

 directions, but often quite crushed ; yet in such a manner that 

 the fragments lay by the side of each other in their natural 

 position. In the same paper I have shown how this fact, as 

 well as some others met with in that cavern, can only be ex- 

 plained by the supposition of effects produced on the animals, 

 when still clothed with flesh and skin, by vast masses of rock. 



The second class of mechanical changes which these bones 

 have undergone, has been effected by the teeth of predatory 

 animals. And again, these changes depend partly on the 

 resistance the bones were calculated to offer, — partly on the 

 character of the animal that attacked them. Such beasts of 

 prey as derive a considerable quantity of nutriment from the 

 bones themselves, and for that purpose are provided with 

 crushing teeth, like the huge hyaenas of the Old World, the 

 remains of which are found in European caves, were want- 

 ing in this part of the globe, and were represented by others, 

 which have left the records of their existence imprinted in a 



