BOCKS. 2GS 



stratification existing between the porphyry ard the argen- 

 tiferous ores in the Saxon mines, (the richest and most 

 important in Germany), that these formations are at any rate 

 more recent than the vegetable remains found i u carboniferous 

 strata and in the red sandstone.* 



All the facts connected with our geological hypotheses on 

 the formation of the earth's crust, and the met amorphism of 

 rocks, have been unexpectedly elucidated by the ingenious 

 idea, which led to a comparison of the slags or scoriae of our 

 smelting furnaces, with natural minerals, and to the attempt 

 of reproducing the latter from their elements. f In all these 

 operations, the same affinities manifest themselves, which 

 determine chemical combinations both in our laboratories 

 and in the interior of the earth. The most considerable part 

 of the simple minerals which characterise the more generally 

 diffused plutonic and erupted rocks, as well as those on which 

 they have exercised a metamorphic action, have been 

 produced in a crystalline state, and with perfect identity, in 

 artificial mineral products. We must, however, distinguish 

 here between the scoriae accidentally formed, and those which 

 have been designedly produced by chemists. To the former 

 belong feldspar, mica, augite, olivine, hornblende, crystallised 

 oxide of iron, magnetic iron in octahedral crystals, and 

 metallic titanium ;J to the latter, garnets, idocrase, rubies, 



* Coustantin von Beust, Ueber die Porpliyrgebilde, 1835, s. 89-96 ; 

 also his BdeucUtung der Werner 'schen Gangtheorie, 1840, s. 6; and C. 

 von Wissenbach, Abbildungen merhciirdiger Gangverhaltnisse, 1836, 

 fig. 12. The ribbon-like structure of the veins is, however, no more 

 to be regarded of general occurrence than the periodic order of the 

 different members of these masses. 



t Mitschcrlich, Ueber die kunstliche Darstellunri der Minerahen, ia 

 the Alhcuidl. der Akademie der Witm. zu Berlin, 1822-3, s. 25-41. 



In scoriae, crystals of feldspar have been discovered by Heine in the 

 refuse of a furnace for copper fusing, near Sangerhausen, and analysed 

 by Kersten (Poggend. Annalen, bd. xxxiii. s. 337); crystals of augite 

 in scoriae, at Sahle (Mitsrherlich in the Abhandl. der Akad. zu Berlin, 

 1822-23, s. 40); of olivin by Seifstrom (Leonhard, BwsaU-Gclrilde, bd. ii. 

 8. 495) ; of mica, in old scoriae of Schloss Garpenberg (Mitscherlich, in 

 Leonhard, op. cit. s. 506) ; of magnetic iron, in the scoriae of Chatillon 

 Bur Seine (Leonhard, s. 441); and of micaceous iron, in potter's clay 

 (Mitscherlich, in Leonhard, op. cit., s. 234). 



[See Ebclmer's papers in Ann. de Cliimie et de PJn/xiq'nc, 1S47 : also 

 Report on tht Crystalline Slays, by John Percy, M.D-, F.1J.S., and William 



