FOREIGN CORRESPONDENCE, 



255 



which the exact age is unknown to me, and which was found in a 

 marine conglomerate of Brazil, has bnt 1*6 thousandth of azote. 



Wh en 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 145 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 Arey, M. de Vibraye says there are three deposits 

 of bones, which are very distinct. The upper and most recent one 

 contain* 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 TJrsus sjielmts, 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 own. 



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, within certain limits, indications of its age ; and 

 furnishes us with another means of determining relative age in the 

 different epochs of our globe. 



