DELESSE — AZOTE IN EOCKS. D 



of the age of any bone from the amount of azote it contains, yet on 

 the whole it diminishes with the age. A similar conclusion also 

 holds good in the case of fossil shells, which, however, often contain no 

 more than some crj^stallized calcite. At p. 217 (p. 67), he points out 

 that the large amount of azote found in some bones of Hyenas from 

 caverns and breccias indicates that they lived in France and England 

 at an epoch when those countries were inhabited by man ; and at 

 p. 231 (p. 80) he applies the same remark to the Bhinoceros and 

 Eeindeer. 



The amount of azote in various recent and fossil vegetables, and the 

 general diminution as we pass from recent to earlier geological periods, 

 are next passed under review. Its occurrence in graphite is an import- 

 ant fact in support of the opinion of that mineral having been de- 

 rived from vegetable substances. In passing to the mineral kingdom, 

 the author remarks, at p. 232 (p. 82), " that it may appear extraordi- 

 nary to look for organic matters in minerals, which are usually crys- 

 talline bodies ; but it is nevertheless easy to prove that they very 

 often contain them, and that even azote occurs in determinable 

 amount." As illustrations he gives the quantity in various sulphu- 

 rets, fluor-spar, rock-salt, various ores of iron, quartz, chalcedony, 

 opal, and such silicates as pyronene, garnet, mica, felspar, &c., as 

 well as in zeolites, gypsum, and carbonates of lime. One of the 

 most striking examples is that of the quartz of granite, which con- 

 tains as much as 0*20 (thousandths) of its weight of azote, which is 

 far more than the amount met with in chaUi-flints, though not so 

 much as in some opals. 



Since the occurrence of azote in various rock-masses is, perhaps, 

 the most interesting result of the author's researches, it will be 

 well to give a more detailed account of the part of the memoir de- 

 voted to that branch of the inquiry. He says that, since erupted 

 roclcs are generally crystalline, the examination of their organic 

 matters should necessarily give results very similar to those obtained 

 in the case of minerals. The experiments were made as much as 

 possible with rocks whose locality and composition were well known, 

 and they were in a great measure collected by the author himself. 

 Bocks having orthoclase-felspar as base, such as granite and porphyry, 

 aU contain organic matters, as is easily proved either by distillation 

 or by determining the amount of azote. It was indeed easy to 

 foresee this, since, as mentioned above, they had been found in quartz, 

 felspar, and mica. The presence of this organic matter is an im- 

 portant fact, and serves to confirm the ideas which the author had 

 already put forth on the origin of these rocks *. Whilst the amount 

 of azote in the granite of Yologne is 0*15, in the quartz -porphyry of 

 Perseigne it is 0*17, and in the minette of "Wakenback it is 0-18 

 (thousandths). The proportion of water is also successively greater 

 in these three rocks ; and one might think that, introduced by infil- 

 tration, the proportion of azote had been thereby augmented. The 

 author, however, shows that in a decomposed quartz-porphyry from 



* '• E^cherches sur I'Origine des Roches," Bull, de la Soc. Gr^ol. de la France, 

 2« ser. XV. p. 718. 



