Metamorphtc Changes of Rocks, Sfc. 113 



direction, and from the nature of the metallic veins and rocky 

 dikes which traverse them. 



The first orographic axis, which runs N.N.E., is composed 

 of two zones of crystalline rocks, but with a stratified structure 

 on the great scale ; that is to say, of rocks whose soluble ele- 

 ments, in precipitating themselves into the crystalline form, 

 were deposited tranquilly, after the manner of a sediment. The 

 first zone of these rocks is composed of gneiss, consequently of 

 felspar and mica ; and the second also of mica, but combined 

 with quartz and talc, the elements of mica-schist and of talc- 

 schist which compose this zone. These rocks being stratified, 

 their inclination and direction are appreciable ; and they are, 

 moreover, the same throughout their whole extent : their forma- 

 tion and their derangements likewise, by elevations, are owing 

 to the same cause, and are principally to be attributed, accord- 

 ing to M. Fournet, to the appearance of granite. 



The second system of mountains, or the second axis of ele- 

 vation, which runs nearly north-west, and so crosses the former, 

 is principally composed of rocks which belong to the transition 

 series. They are compact limestones, rocks of the greywacke 

 series (traumates) with vegetable markings, conglomerates, &c. 

 M. Fournet conceives that he can refer this axis or line of di- 

 rection of uplifting forces to the second type of elevation esta- 

 blished by our colleague M. Elie de Beaumont, adducing as 

 examples the round eminences of the Vosges and the hills of 

 Bocage. It is in the ancient depressions of this system that the 

 coal formation presents itself, like so many islands, and here, 

 too, it is that the metallic and metalliferous veins are found. 

 M. Fournet attributes this axis to the elevation of quartzose 

 porphyries. 



The third axis or system of elevation which shews itself even 

 tothe north of Tarare,or the valleys of Tardive and of Azergue, 

 runs straight from south to north : but it appears to us much 

 less satisfactorily determined than the previous ones, both as it 

 regards the rocks which compose it, and also respecting those 

 which have upraised them. According to the author, it is owing 

 to the consequences of the eruption of quartzose porphyries, 

 but under other declinations, and has been terminated by the 

 eruption of the trap-rock, consequently augitic or horn1)lende 



VOL. XXIV. NO. XLVII. — JANUAllVT 1838. H 



