cllV NOTES. 



and kindly the first recognition that " all the volcanoes of the Andes have their 

 seat in a porphyry which is a peculiar rock, and belongs essentially to volcanic 

 formations." (Abhandlungen der Akademie der Wiss. zu Berlin, for 1812 

 1813, S. 131, 151, and 153.) I may, indeed, have expressed the phenomenon 

 with most generality; hut, as early as 1789, Nose, whose merits were long un- 

 recognised, had, in his " Orographic Letters," described the volcanic rock of the 

 Siebengebirge as " a peculiar kind of Rhenish porphyry, nearly allied to basalt and 

 porphyritic schist." He says that this formation is particularly characterised 

 by glassy felspar, which he proposes to call sanidine, and that, by its age, it 

 belongs to the middle-fketz strata. (Niederrheinische Reise, Th. I. S. 26, 28, 

 and 47; Th. II. S. 428.) I am inclined to think that Von Buch was mistaken 

 in stating that Nose recognised this porphyritic formation (which he not very 

 happily calls " granite-porphyry ") and basalts as being younger than the most 

 recent floetz-strata. The great early-removed geognost said: " The whole rock 

 ought to be named from the glassy felspar (therefore sanidine-porphyry), if it 

 had not already the name of trap-porphyry." (Abh. der Berl. Akad. for 1812 

 1813, S. 134.) The history of the systematic nomenclature of a science is 

 not without some importance, inasmuch as it reflects the succession of prevailing 

 opinions. 



( WI ) p. 427. Humboldt, Kleinere Schriften, Bd. i. Vorrede, S. iii. v. 



( M2 ) p. 428. Leop. von Buch, in Poggendorff's Annalen, Bd. xxxvii. 1836, 

 S. 188 and 190. 



C 88 ) p. 428. Gustav Rose in Gilbert's Annalen, Bd. 73, 1823, S. 173, and 

 Annales de Chimie et de Physique, t. xxiv. 1823, p. 16. Oligoclase was first 

 proposed as a new mineral species by Breithaupt. (Poggendorff's Annalen, Bd. 

 viii. 1826, S. 238.) Subsequently oligoclase appeared to be identical with 

 a mineral which Berzelius observed in a granite dyke in gneiss, near Stock- 

 holm, and which, on account of similarity of chemical composition, he had called 

 " Natron Spodumen." (Poggendorff's Ann. Bd. ix. 1827, S. 281.) 



( 594 ) p. 429. See Gustav Rose on the granite of the Riesengebirge, in Pogg. 

 Ann. Bd. Ivi. 1842, S. 617. Berzelius had only found oligoclase, his " Natron 

 Spodumen," in a granite dyke ; it is in the above-cited memoir that it is first 

 spoken of as an ingredient of granite (of the rock itself). Gustav Rose deter- 

 mined oligoclase by its specific weight, the larger quantity of lime contained in 

 it in comparison with albite, and its greater fusibility. A specimen, of which 

 he had found the specific gravity 2*682, was analysed by Rammelsberg. (Iland- 

 wbrterbuch der Mineral. Suppl. i. S.I 04 ; and G. Rose, Ueber die zur Granitgruppe 

 gehorenden Gebirgsarten, in der Zeitschr. der Deutschen geol. Gesellschaft, Bd. 

 i. 1849, S. 364.) 



