FLUORIDE OF CALCIUM IN WATER. 747 



the age of bones, and of the rocks containing them, by the per-centage of fluorine 

 in the former.* This idea, however, is certainly unwarranted. In the bones of 

 five fossil animals, including the Plesiosaurus and Ichthyosaurus, Giraedin and 

 Peeissek found from one to two per cent, of fluoride of calcium ;f -whilst in those 

 of the recent ox, Berzelius found nine per cent.| In the ancient bones there was 

 thus, instead of a much higher per-centage, seven per cent, less of fluorine than in 

 the recent bones. Many other objections might be made to Mr Middleton's view. 

 Those who deny the existence of fluorine in recent bones, consider the whole 

 amount of that element found in ancient buried ones, as in some way or other a 

 product of fossilisation. According to those, on the other hand, who affii-m the 

 presence of that element in recent organisms, only a portion, at most, of the fluo- 

 rine found in osseous remains has been added since they ceased to be parts of 

 living animals. It is impossible, however, to separate the two questions. We 

 have no data from which to determine whether or not the bones of an extinct 

 animal contained fluorine during its life, and, if it did, how much was present. 

 It wiU be sufficient, therefore, if I consider what progress has been made in an- 

 swering the one question, How does fluoride of calcium come to be present in 

 bones, either recent or fossil ? 



Three replies have been proposed to this query. 1st, That of Dr Falconer, 

 already referred to, which, taking for granted that fossU bones contain more fluo- 

 rine than they possessed whilst parts of living animals, assumes, or rather sug- 

 gests as possible, that phosphate of lime has been transmuted into fluoride of 

 calcium. § 2d, That of Liebig, which, going on exactly an opposite assumption, 

 takes for granted (if I understand him aright) that bones of living antediluvian 

 animals contained the same proportion of fluorine which we find in then* fossil 

 remains ; and refers its greater abundance in these, either to its having been 

 present in larger quantity in the food of their living possessors, than it is in that 

 of existing animals, or to its having been appropriated to a larger amount from 

 it II The third is that of Mr Middleton, who supposes every bone to possess 

 normally two per cent, of fluoride of calcium, and considers all above that which 

 a fossil bone contains, as added to it whilst buried in the earth, by the infiltra- 

 tion of water containing that salt held in solution by some unknown solvent. 



It is unnecessary to discuss the first and second propositions referred to. It 

 is impossible, in the present state of our knowledge, either to prove or to disprove 

 them. The idea of transmutation of a phosphate into a fluoride, was doubtless 

 suggested solely because there seemed no other way of accounting for the accu- 

 mulation of fluorine, and will be abandoned, if it shall appear that recognized 



* Quarterly Journal of Geological Society, vol. i., p. 216. 



t Annales de Chimie, 1843, pp. 370-78. { Ibid., t. Ixi., p. 257. 



§ Literary Gazette, 1843, p. 779. 



II Chemistry of Agriculture, 3d edition, p. 123. 



