26 Relations of Trap-Rocks ivith Ores of Copper. 



of these ores, under a form sufficiently subtile to penetrate 

 into all the fissures of a formation, to saturate all the mineral 

 mass, and become insulated in wide veins. This Rio repo- 

 sitory bears, indeed, all the characters of a slow generation, 

 by the prolonged action of vapours analogous to those which 

 bring the oligistic iron into the craters of volcanoes. The 

 lustre, the geodes incrusted with crystals, the perfect isola- 

 tion of the crystals of pyrites which formed special groups, 

 and the corrosion of these pyrites, which are often trans- 

 formed into oligistic iron ; all these details seem to combine 

 in indicating the prolonged action of metalliferous vapours. 

 We see that, in many cases, the oligistic iron ; when in the 

 micaceous form which, under the hammer, aftbrds a light 

 and brilliant powder, is posterior to the oligistic iron, which 

 is compact or in binoternary crystals. Is not this same sub- 

 teri'anean action further evident in the semi-crystalline re- 

 pository of Framont, which has pi'oduced the repositories of 

 the Harz and Nassau, which differ from it only in their less 

 crystalline nature % Ought not the lithoid oligistic iron, 

 which impregnates the schalstein, blatterstein, and gabbro, 

 be ascribed to the same causes, which are here marked by 

 the same conditions of position, and finally the red hue of 

 the stratified rocks, such as the red clay-slate, the gallestri, 

 mattoni, <irc. 



By generalising this theory, we shall be led to even more 

 extended conclusions. In certain sedimentary formations, 

 we find earthy oligistic irons concentrated or disseminated 

 in the red-coloured rocks. Formations of the old and new 

 red sandstone, the sandstone of the Vosges, the varied co- 

 loured mai'ls, and generally the gypseous and saliferous marls 

 of the secondary or tertiary formations, present us with 

 numerous and well-developed examples, either of the general 

 or partial coloration of deposits by oligistic iron. Among 

 these deposits we find beds of concentrated ores, compact or 

 oolitic (Lavoulte, Lavei'pillere, Privas, &c.,) and in these beds 

 shells, themselves transformed into compact or even crys- 

 talline ores. 



What are the phenomena which could have accumulated 

 in particular beds, or disseminated, through entire formations, 



