ROCKS. 201 



found in rocks, which have some claim to be considered as 

 mica slate, and in the schistose group in the western part of 

 the island of Elba, near the promontory of Calamita, and the 

 Fichtelgebirge in Baireuth, between Lomitz and Markleiten.* 

 Jasper, which,! as I have already remarked, is a production 

 formed by the volcanic action of augitic porphyry, could only 

 be obtained in small quantities by the ancients, while another 

 material, very generally and efficiently used by them in the 

 arts, was granular or saccharoidal marble, which is likewise 

 to be regarded solely as a sedimentary stratum altered by ter- 

 restrial heat and by proximity with erupted rocks. This opin- 

 ion is corroborated by the accurate observations on the phe- 

 nomena of contact, by the remarkable experiments on fusion 



distinct cause, but not losing their stratification, tliey somewhat resem- 

 ble in their physical structure a biaud of half-consumed wood, in which 

 we can follow the traces of the ligneous fibers beyond the spots which 

 continue to present the natural characters of wood." (See, also, the 

 Annates des Sciences Naturclles, t. xiv., p. 118-122, and von Dechen, 

 Geognosie, s. 553.) Among the most striking proofs of the transforma- 

 tion of rocks by Plutonic action, we must place the belemnites in the 

 Bchists of Nufibnen (in the Alpine valley of Eginen and in the Gries- 

 glaciers), ani^the belemnites found by M. Charpentier in the so-called 

 primitive limestone on the western descent of the Col de la Seigne, be- 

 tween the Enclove de Monjovet and the chdlet of La Lanchette, and 

 which he showed to me at Bex in the autumn of 1822 {Annales de 

 Chimie, t. xxiii., p. 262). 



* Hoffmann, in Poggend., AnnaJen, bd. xvi., s. 552, " Strata of tran 

 sition argillaceous schist in the Fichtelgebirge, which can be traced for 

 a length of 16 miles, are transformed into gneiss only at the two ex- 

 tremities, where they come in contact with granite. We can there 

 follow the gradual formation of the gneiss, and the development of the 

 mica and of the feldspathic amygdaloids, in the interior of the argilla- 

 ceous schist, which indeed contains in itself almost all the elements of 

 these substances." 



t Among the works of art which have come down to us from the an 

 cient Greeks and Romans, we observe that none of any size — as columns 

 or large vases — are formed from jasper; and even at the present day, 

 this substance, in large masses, is only obtained from the Ural Mountains. 

 The material worked as jasper from the Rhubarb Mountain (Raveniaga 

 Sopka), in Altai, is a beautiful ribboned poi-phyry. The word jasper 

 is derived from the Semitic languages ; and from the confused descrip- 

 tions of Theophrastus (De Lapidibus, 23 and 27) and PUuy (xxxvii., 8 

 and 9), who rank jasper among the " opaque gems," the name appears 

 to have been given to fragments of jaspachat, and to a substance which 

 the ancients termed jasponyx, which we now know as opal-jasper. 

 Pliny considers a piece of jasper eleven inches in length so rare as to 

 require his mentioning that he had actually seen such a specimen : 

 " Magnitudinem jaspidis undecim unciarum vidimus, formataiuque iude 

 effigiem Neronis thoracatam." According to Theophrastus, the stone 

 which he calls emerald, and from which large obelisks were cut, must 

 have been an imperfect jasper. 



