FOREIGN CORRESPONDENCE. 
255 
which the exact age is unknown to me, and which was found in a 
marine conglomerate of Brazil, has but 1*6 thousandth of azote. 
When bones have been buried under the same condition the quantity 
of azote becomes better comparable ; and then it varies, especially in 
relation to their age. 
According to the observations of M. Lartet, the human bone of 
Aurignac, above mentioned, was associated with extinct species of ani- 
mals, especially of the reindeer and rhinoceros. It therefore became of 
interest to discover the quantity of azote in the bones of those animals. 
I have obtained 14'8 for the reindeer, and 14: o for the rhinoceros 
of Aurignac. That is to say, nearly the same proportion as for the 
human cubitus found in the same deposit. Hence, analysis seems to 
indicate that these extinct animals were contemporaneous with man. 
In the grotto of Arcy, M. de Yibraye says there are three deposits 
of bones, which are very distinct. The upper and most recent one 
contains unmistakeable traces of the habitation of man, and of animals 
still represented in the vicinity. In a human bone which came thence, 
I found still twenty-four thousandths of azote. The middle deposit 
contains bones of extinct species, particularly the reindeer, in which 
there is 14 3 of azote : these last are enveloped in a red clay, with a 
great number of celts and of flint implements. The lower deposit con- 
tains bones of Ursiis sj^elcens, which, contain no more than 10'4 of azote. 
It is therefore very evident that the azote varies in the bones from 
these deposits according to their age ; and that it successively 
diminishes as the age itself increases. 
The caverns and osseous breccias contain bones of the hyena, stag, 
ox, horse, and rhinoceros, which have an equal, or nearly equal, 
proportion of azote to those of certain human bones of great antiquity. 
Analysis proves, consequently, that these animals, belonging to 
extinct species, have lived on our earth at an epOch not fai removed 
from our o^vn. 
To sum up : a fossil bone is subject to very complex alterations. 
The porosity and density augment ; its bony substance is destroyed ; 
and the proportion of calcareous salts is more or less modified, or 
altogether destroyed. In the first phase of decomposition, a bone 
retains a great part of its osseine, effervesces slowly in acid, and loses 
a little of its carbonate of lime. In the last phase the bony substance 
has almost altogether disappeared : it is sharp to the taste, and effer- 
vesces violently in acid. At this period its carbonate of lime tends 
generally to augment more rapidly than the phosphate. Sometimes 
it still undergoes other metamorphoses, which completely alter its 
chemical composition, although its form remains unchanged. 
The testing of azote, then, contained in a fossil bone, permits us to 
control and verify^ the assertions of archaeology and geology. It can 
even afford us, wHthin certain Hmits, indications of its age ; and 
furnishes us with another means of deteraiining relative age in the 
different epochs of our globe. 
