TRANSLATIONS AND NOTICES 



GEOLOGICAL MEMOIRS. 



The QuARTziFEROus PoRPHYRiES, according to their Nature, 

 their Distribution, their Relation to Normal Stratified 

 and Unstratified Rocks, as well as Mineral Veins. By 

 Dr. GusTAv Leonhard of Heidelberg, pp. 212. 8vo. Stutt- 

 gart, 1851. With 2 Lithographs, 5 Plates of coloured Sections 

 and 12 Woodcuts. 



Die Quarz-fuhrenden Porphyre, iiach ihrem Wesen, ihrer 

 Verbreitung, ihrem Verhalten zu ahnormen and normalen 

 Gesteinen, so wie zu Erzgangen. Von Gustav Leonhard. 



In drawing the attention of our readers to this work, we may men- 

 tion that it is the first attempt hitherto made to bring together the 

 history of the porphyritic rocks and the literature connected there- 

 with, as also to describe the various localities where the Quartziferous 

 Porphyries have been observed, as well as their relations to other 

 rocks, sedimentary and non-sedimentary. 



The ancients, it is well known, reckoned Porphyry amongst their 

 marbles. Pliny remarked, that " the porphyritic marble, which was 

 quarried in Egypt, has a reddish colour." The beautiful Porphyry, 

 so much used in the classic ages, and of which many important works 

 of art were constructed, was derived in all probability from Upper 

 Egypt, and not, as Roziere formerly supposed, from Mount Sinai. 



Pliny also alludes to the white spots in the Porphyry, for which 

 reason it was called Leucosticos or Leptosephos. Lucan calls the rock 

 Lapis purpureus, on account of its red colour, which was peculiarly 

 appropriate to that of Egypt. 



Even in the sixteenth and seventeenth centuries, the word Por- 

 phyry was used by naturalists in the same vague and uncertain sense ; 

 it had a purely technical signification. Agricola reckoned it amongst 

 his Marbles, under which name were at that time included all rocks 

 capable of being polished. The artists of Italy distinguished it ac- 

 cording to its colour, Porfido rosso, Forfido nero, Forfido verde an- 

 tico, &c., terms of which even the most learned, as Cronstedt, Lin- 

 nseus, Wallerius, Saussure, &c., have made use. 



Some writers have been induced, in consequence of the great hard- 

 ness of certain kinds of Porphyry, to class it amongst the precious 

 stones (Briickemann) . 



vol. VIII. — PART II. B 



