456 The American Naturalist. [May, 
As has been established in the table on page 447, the relation 
between the weight of the phosphoric acid and the weight of 
fluorine and water was in the neighborhood of 193 in mod- 
ern bones, while it became reduced to 31 in the average of 
quaternary bones, and 19 for their average in bones of the 
pliocene period. Therefore, the animal bones found in the 
sands of Billancourt present a relative proportion of fluorine 
intermediate between the average of the quaternary bones 
and those of the pliocene, that is to say, for the one was 23.9, 
for the other, 19.4. 
On the contrary, for the human tibia submitted to analysis, 
the relation is raised to 168.9 and it is, therefore, 8 times greater 
than in the animal bones, and is only slightly lower than that 
of the modern bones. We can, therefore, conclude that the 
human bone belongs to an age much more recent than those of 
the animal, and that if it was really in the ancient gravels of 
the Seine in the neighborhood of the found bones of the qua- 
ternary animal, it was only by reason of a natural change of 
position or else the result of accident. 
It is believed that this new method of control may prove to 
be of utility in determining the problems relative to the an- 
tiquity of man. It often happens that in the excavations 
made in prehistoric stations, one encounters human bones as- 
sociated with animal bones, whether in alluvial deposits, 
caverns or rock-shelters. If the man and the animal in these 
deposits were contemporaneous, their bones, having been ex- 
posed to the same influence and submitted to the same 
transformation, ought to have approximately the same 
proportion of phosphoric acid and fluorine. But if the 
human bones are of an age much more recent than those 
of the animal and have been introduced either by accident 
or fraud, we can, perhaps, find the proof. by this chemi- 
cal analysis and be able to detect the error by the difference 
in the relative proportions between their phosphoric acid and 
fluorine. 
(To be Continued.) 
