4:70 COSMOS. 



more profound and less prejudiced character led to the recog- 



diffevenfc zones do not always present the same (mineralogical) composi- 

 tion, or the same component parts. Sometimes we find trachytes, 

 properly so called, characterised by the glassy felspar, as at the Peak 

 of Tenerifie and in the Siebengebirge near Bonn, where a little albite ia 

 associated with the felspar, felspathic trachytes, which, as active 

 volcanoes, exhibit abundance of obsidian and pumice ; sometimes 

 melaphyre, and doleritic mixtures of labradorite and augite, more 

 nearly resembling the basalt formation, as at Etna, Stromboli, and 

 Chimborazo ; sometimes albite with hornblende prevails, as iu the 

 lately so-called andesites of Chili and the splendid columns, described 

 as dioritic-porphyry, at Pisoje near Popayan, at the foot of the volcano 

 of Purace", or in the Mexican volcano of Jorullo ; finally, they s-re some- 

 times leucite-ophyrs, a mixture of leucite and augite, as in the Somma, 

 the ancient wall of the crater of elevation of Vesuvius." By an acci- 

 dental misinterpretation of this passage, which shows many traces of 

 the then imperfect state of geological knowledge (felspar being still 

 ascribed to the Peak of Teneriffe instead of oligoclase, labradorite to 

 Chimborazo, and albite to the volcano of Toluca), that talented investi- 

 gator Abich, who is both a chemist and a geologist, has erroneously 

 attributed to myself the invention of the term andesite as applied to a 

 trachj'tic, widely-dispersed rock, rich in albite (Pogysnd. Ann., 

 Bd. ii, 1840, s. 523), and has given the name of andesine to a new 

 species of felspar, first analysed by him, but still somewhat enigmati- 

 cal in its nature, "with reference to the mineral (from Marmato, uear 

 Popayan) in which it was first observed." The andesine (pseudo-albite 

 in andesite) is supposed to occupy a middle position between labradorite 

 and oligoclase ; at the temperature of 55.7 its specific gravity is 2.733', 

 while that of the andesite in which the andesine occurred is 3.593. 

 Gustav Rose doubts, as did subsequently Charles Deville (Etudes de 

 Lithoiogie, p. 30), the individuality of andesine, as it rests only on a 

 single analysis of Abich, and because the analysis of the felspathic 

 ingredient in the beautiful dioritic-porphyry of Pisoje near Popayan, 

 brought by me from South America, which was performed by Francis 

 (Poggend., Bd. lii, 1841, s. 472) in the laboratory of Heinrich Rose, 

 while it certainly shows a great resemblance to the andesine of Mar- 

 mato, as analysed by Abich, is, notwithstanding, of a different com- 

 position. Still more uncertain is the andesine in the syenite of 

 the Vosges (from the Ballon de Servance, and Coravillers, which Delesse 

 has analysed). Compare G. Rose, in the already often-cited Zeitschrift 

 cler Deutscken geologischen Gesdlschaft, Bd. i, for the year 1849, s. 369. 

 It is not unimportant to remark here that the name andesine, intro- 

 duced by Abich as that of a simple mineral, appears for the first time 

 in his valuable treatise entitled, Beitrag zur Eenntniss des Feldspaths 

 (in Poggend. Ann., Bd. 1, s. 125, 341, Bd. li, s. 519), in the year 

 1840, which is at least five years after the adoption of the name ande- 

 site, instead of being prior to the designation of the mineral from which 

 it is taken, as has been sometimes erroneously supposed. In the forma- 

 tions of Chili which Darwin BO frequently calls andesitic granite 



