268 COSMOS. 



the simple Diiiicrals which characterize the more generally 

 diffused Plutonic and erupted rocks, as well as those on whicli 

 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 be- 

 tween the scoriEB accidentally formed, and those which have 

 been designedly produced by chemists. To the former belong 

 feldspar, mica, augite, olivine, hornblende, crystallized oxyd 

 of iron, niagnetic iron in octahedral crystals, and metallic 

 titanium ;* to the latter, garnets, idocrase, rubies (equal in 

 hardness to those found in the East), olivine, and augite. T 

 These minerals constitute the main constituents of granite, 

 gneiss, and mica schist, of basalt, dolerite, and many porphy- 

 ries. The artificial production of feldspar and mica is of most 

 especial geognostic importance with reference to the theory of 

 the formation of gneiss by the metamorphic agency of argilla- 

 ceous schist, which contains all the constituents of granite, 



* la scoricD, ciystals of feldspar have been discovered by Heine in 

 the refuse of a furnace for copper fusing, near Saugerhausen, and ana- 

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

 augite in scorice, at Sable (Mitscherlich, in the Abhandl. der Akad. zn 

 Berlin, 1822-23, s. 40); of olivine by Seifstrom (Leonbard, Basalt-Gc- 

 Hide, bd. ii., s. 495); of mica in old scoriae of Scbloss Garpenberg 

 (Mitscberlicli, in Leonbard, op. cit., s. 503); of magnetic iron in tbo 

 ecoricB of Chatillon sur Seine (Leonbard, s. 441); and of micaceous iron 

 in potter's clay (Mitscberlicli, iu Leonbard, op. cit., s. 234). 



[See Ebebner's papers in Ann. de Chimie et de Physique, 1847 ; also 

 Report on the Crystalline Slags, by Jobn Percy, 1\I.D., F.R.S., and 

 WiUiam Hallows Miller, M.A., 1847. Dr. Percy, in a communication 

 witb which he bas kindly favored me, says that tbe minerals wbicb he 

 lias found artificially produced and proved by analysis are Humboldtil- 

 ite, geblenite, olivine, and magnetic oxyd of iron, in octabedral crys- 

 tals. He suggests tbat tbe circumstance of the production of geblenite 

 at a higb temperature in an iron furnace may possibly be made avail- 

 able l)y geologists in explaining tbe formation of tbe rocks in wbicb tbe 

 natural mineral occurs, as in Fassatbal in tbe Tyrol.] — Tr. 



t Of minerals purposely produced, we may mention idocrase and 

 garnet (Mitscberlicli, in Poggend., Annalen der Physik, bd. xxxii., s. 

 340); ruby (Gaudin, in the Complcs Rendiis de VA.cadimie de Science, 

 t. iv.. Part i., p. S99) ; olivine and augite (Mitscberlicli and Bertbier, iu 

 the Annalcs de Chimie et de Physique, t. xxiv., p. 376). Notwitbstand 

 ing tbe greatest possible similarity in crystalline form, and perfect iden 

 tity in chemical composition, existing, according to Gustay Rose, be- 

 tween augite and hornblende, hornblende has never been found accom. 

 panying augite in scoriae, nor have chemists ever succeeded in artificial- 

 ly producing either hornblende or feldspar (Mitscberlicli in Pos^gend., 

 Annalen, bd. xxxiii., s. 340, and Rose, Reise nach dem Ural, bd. ii., s 

 358 und 363). See, also, Beudant, in XheMem. de f Acad, des Sciences, 

 t. viii., p. 221, and Becquerel's ingenious experiments in bis Trail' .ts 

 r Fdectric'tS, t. i., p. 334 ; t. iii., p. 218; and t, v., p. 148 and 183 



