ANNIVERSARY ADDRESS OF THE PRESIDENT. Ixxiii 



have enabled him to give abundant detail on the characters of the 

 crystalUne central range of the Savoy Alps. The time-honoured 

 protogcne is fully confirmed by him in its original dignity of the 

 chief prop or centre-piece of the v^^hole, although, since the studies 

 of M. Delesse, it is allowed that it belongs, as a distinct variety, to 

 the group of the granites. It consists of five minerals, viz. quartz, 

 orthoclase, oligoclase, a mica with iron-oxide base, and talc, and, 

 as a general rule, appears to possess a more truly granitic character 

 in the central parts of the formation, a schistose one towards the 

 flanks. The presence of this second felspar, oligoclase, in these great 

 Alpine nuclei is a point of great interest in the comparison of these 

 with other granite rocks, as well as in the chemical changes and 

 disintegration to which its composition peculiarly exposes it. As 

 regards the gisement or geognostic position of this rock, he states his 

 opinion, 1st, that it is stratified, and, 2ndly, that it never penetrates 

 in the form of veins or dykes into other strata, as does the true 

 granite, which is found, although rarely, here and there in this 

 Alpine district — moreover, that by the forms in which it weathers 

 it may be distinguished, even at a distance, from the granites, and 

 that, although formed at a very ancient period in the history of the 

 globe, it has only made its appearance at the surface within a com- 

 paratively recent time. 



"When we follow him into the domain of theory, the Geneva pro- 

 fessor leads us into a misty region of somewhat audacious specula- 

 tions. To him the commonly received view of metamorphism is a 

 grossly exaggerated mysterious process, which he conceives to be 

 entirely incapable of having formed the crystalline schists. He 

 carries us back rather to a primeval period, when he supposes the 

 whole of the now existing surface waters to be floating as vapour in 

 the atmosphere, and to exert a pressure of 250 atmospheres. Added 

 to this he infers that the subterranean water would make as much 

 more, and would thus give a total pressure of 500 atmospheres. The 

 carbonic acid which has since been fixed in the coal-beds would not 

 add greatly to the weight of this crushing atmosphere ; but the 

 same gas which has been locked up in the limestones and other 

 carbonates is estimated by him at 210 atmospheres more, and would 

 thus give a grand total of 710 atmospheres which then weighed upon 

 the surface of the earth. 



Under this pressure, at which water would only boil at 480° C, 

 or 896° Pahr., and when the temperature of the crust began gradually 

 to diminish, the first precipitations and erosions would form a sedi- 

 ment which would be highly crystalline, and would in fact produce 

 the granites and protogenes. Then, as the pressure and temperature 

 were further decreased, the crystallization would be less marked, 

 whilst the stratification would be more pronounced, and there would 

 be dejiosited successively the crystalline schists and, at length, the 

 clay slates. As for the original rock from which this fiirst degrada- 

 tion took place, it would be lava ; and our author, overriding the 

 great and marked differences between the two magmas of Durocher, 



VOL. XXIV. / 



