Dr. J. L. Smith on Fluorine in Fossil Bones. 99 



II. Source of Fluorine in Fossil Bones.* 



The analyses of fossil bones communicated by MM. Girardiii 

 and Preisser to the Academie des Sciences, Oct. 1842, afford the 

 only well detailed numerical results of the composition of this 

 class of bones that we possess. The authors appear to have be- 

 stowed considerable care upon their research, and their estimate 

 of the proportion of fluoride of calcium present was as follows : 



Per cent. 



A metacarpal bone of a Bear from the cavern of Mialet, 1-09 



Tusk of an Elephant, ...... 3-64 



Vertebra of a Plesiosaurus, ..... 2*11 



The great bone of the Poekilopleuron Bucklandii, . 1-50 



Rib of an Ichthyosaurus, ,1-02 



Head of the same Ichthyosaurus, .... 1-65 

 Bone of the Lamenton from the tertiary formation in the 



environs of Valognes, ..... 9-12 



This fluoride would appear to form a distinguishing mark be- 

 tween fossil and recent bones, although Berzelius has found it to 

 exist in these latter, and Marchand in some recent experiments 

 mentions the same fact ; still many other chemists have not suc- 

 ceeded in detecting it. MM. Girardin and Preisser suppose that 

 it was owing to some accidental circumstances that Berzelius was 

 enabled to discover it in the cases that he examined, they having 

 in no instance found it, although carefully sought for. My ex- 

 perience tends to confirm Berzelius in his statement, having in 

 several cases obtained most decided evidence of its presence in 

 recent bones, but in very minute quantity. In many instances I 

 failed to detect it, and attribute the failure more to the minute- 

 ness of the quantity than to the total absence of it. 



I would here remark, that in examining for fluorine in the or- 

 dinary way, by testing the effects of the hydrofluoric acid (liber- 

 ated by the action of sulphuric acid) upon waxed glass with char- 

 acters traced out, the process requires some precaution when the 

 quantity present is supposed to be very small, for I have been able 

 in several instances to obtain a permanent delineation of the char- 

 acters traced, without the presence of fluorine. In these cases it 

 is caused by the action of the vapors of either sulphuric or hydro- 



* This and the two following articles are extracts from communications made to 

 the Association of American Geologists and Naturalists, at Washington, May, 1844. 



