clxviii NOTES. 



der deutschen geologischen Gesellschaft, Bd. i. for 1849, S. 369. It is not un- 

 important to recall here that the name of andesine is first adduced by Abich, as 

 that of a simple mineral, in his comprehensive memoir entitled, " Beitrag zur 

 Kenntniss des Feldspaths" (Poggend. Ann. Bd. 1. S. 125 and 341; Bd. li. S. 

 519), in 1840, at least five years after the introduction of the word andesite, not 

 antecedently to it, as has been sometimes erroneously stated. The formations in 

 Chili, which Darwin so often calls " andesitic granite " and " andesitic porphyry," 

 rich in albite (Geological Observations on South America, 1846, p. 174), may 

 very well also contain oligoclase. Gustav Rose, whose memoir " Ueber die Nomen- 

 clatur der mit dem Griinsteine und Grunsteinporphyr verwandten Gebirgsarten " 

 (in Poggend. Ann. Bd. xxxiv. S. 1 30) appeared in 1835, neither then nor 

 subsequently used the word " andesite," the definition of which, according to our 

 present knowledge of the nature of the ingredients, would be not " albite with 

 hornblende," but, in the Cordilleras of South America, " oligoclase with augite," 

 The already antiquated story of this tern), which I have, I fear, treated at too 

 much length, concurs with many other examples in showing that, in the course 

 of the development of our physical knowledge, the descriptive sciences may gain 

 by th-3 stimulus to observation sometimes afforded by erroneous or inadequately 

 grounded distinctions (as in the tendency to reckon varieties as species). 



( 61 ) p. 436. As early as 1840, Abich described oligoclase-trachytes from 

 the summit-rock of Kasbegk, and from a part of Ararat (Abich, " Ueber die 

 Natur und die Zusammensetzung der Vulkan-Bildungen, S. 46); also, as early 

 as 1835, Gustav Rose (Poggend. Ann. Bd. xxxiv. S. 30) expressed himself 

 cautiously to the effect: " that hitherto in his determinations he had not taken 

 account of oligoclase and pericline, which yet are probably also components." 

 The belief which was formerly much entertained, that a decided predominance 

 of augite or of hornblende would also allow us to conclude as to a determinate 

 species in the felspathic series, glassy orthoclase (sanidine), labradorite, or 

 oligoclase, seems to be much shaken by a comparison of the Chimborazo- and 

 Toluca-rocks, of the trachytes of the fourth and third divisions. In basaltic 

 formations, hornblende and augite are often both equally abundant; that is by 

 no means the case in trachytes; but, in a very few instances, I have found 

 augite-crystals in Toluca-rock, and some crystals of hornblende in portions of 

 the Chimborazo-, Pichincha-, Purace'-, and Teneriffe-rock. Olivines, which are 

 so exceedingly rarely wanting in basalts, are as rarely to be found in trachytes 

 as they are in phonolites; and yet we sometimes see, in particular lava-currents, 

 olivines form in quantity by the side of augites. Mica is generally very unusual 

 in basalt; and yet some basaltic summits of the Bohemian Mittelgebirge, first 

 described by Reuss, Freiesieben, and myself, contain it in quantities. It is pro- 



