1844.] 



433 



Hills, and a bone of the Anoplotlierium ; the latter being given by 

 Lassaigne : — • 



In comparing together the quantities of fluoride of calcium in 

 bones of different periods, we should be guided, I apprehend, by 

 the proportion it bears, in each specimen, to the fixed basis of the 

 bone, phosphate of lime, a substance which seems but little liable 

 to variation in amount. The comparisons stand thus : — 



Phosphate of Lime. Fluoride of Calcium. 



Recent bone - - 52-11 - . - 1-99 



The Greek's bone - - 70-01 - - . 5-04 



The Sewalik fossil bone - 78-00 ... 10-65 

 The Anoplotherium bone - 37-00 - - . - 15-00 



When the animal matter, entirely obliterated in the fossil bones, 

 has been suppressed in the recent bones, we have : — 



Phosphate of Lime. Fluoride of Calcium. 



Recent bone - - 77*84 - . _ 2-97 



The Greek's bone - - 78-55 - - - 5*62 



The Sewalik fossil bone - 78-00 - - - 10-65 



The Anoplotherium bone - 37-00 - - - 15-00 



If now, for convenience of computation, we represent the phos- 

 phate in each case by 100, we obtain the following ratios of the 

 fluoride : — 



Recent bone - - - 3-81 



The Greek's bone . - 7-15 



The Sewalik fossil bone - 13-01 



The Anoplotherium bone - 40*54 



Now, as the age of the Grreek's bone is known to be 2000 years, 

 we obtain, if my hypothesis be just, the following values, in time, of 

 the above ratios of the fossil bones : viz. the Sewalik fossil, 7700 

 years ; the Anoplotherium, 24,200 years. 



