302 The American Naturalist. [April, 
say, in a quantity so small that the most delicate mechanism 
and operation were required to find it, and emphasizing this on 
page 70, he declines to give any analytic method by which he 
can determine the exact quantity of this salt in the bones 
tested. The results of analyses of Von Bibra were to the same 
effect. Heintz believes that he had found in the ash of the 
human femur from three to five per cent of the fluoride of cal- 
cium; while Zaleski made it less than one per cent. 
The discoveries of prehistoric man in later times has ren- 
‘dered this investigation of greater interest than ever before. 
No prehistoric anthropologist of serious application, but has 
greatly desired some test which might even, in a measure, de- 
termine the relative, if not the actual, antiquity of bones found 
in prehistoric graves. To these persons it will be welcome 
news that the discoveries of the existence of fluorine in differ- 
ent proportions in recent bones and those of antiquity will 
furnish a test of their respective ages, however slight and un- 
certain it may be. It may be only partial, cannot be de- 
pended upon in all cases, but will be, nevertheless, a source of 
gratification if it be a step towards the solution of a contro- 
verted point. It may be freely conceded that animal bones 
deposited in one locality may possess a greater quantity of 
flourine than they would have if deposited in another. The 
condition of their surroundings, the presence and association 
of different salts may produce a decided effect upon the results. 
But there may be cases in which these differences do not exist, 
and hence, this test may be invoked with considerable benefit. 
A deposit of human and animal bones may be mingled to- 
gether, the fossilization of the latter may be determined from 
other knowledge of their antiquity, while the deposit, being 
in the same locality, subjected to the same conditions, having 
the presence of the same chemical constituents, the difference 
in fluorine of the various bones may afford in some degree, 
possibly slight, a test as to the antiquity of human bones. 
Such a test and comparison was sought to be made by the 
writer in the case of the deposit of animal bones found at 
Natchez by Dr. Dickeson. Along with them was a fragment 
of a human pelvis. While they were not actually touching 
