TRUE VOLCANOES. 477 



leucite raise some chemical difficulties to the explanation of 

 the mode in which the integumental covering is formed. 

 Leucites, partly detached, ace ording to Scacchi, and partly- 

 mixed with lava, were extremely abundant in the recent 

 eruptions of Vesuvius in 1822, 1828, 1832, 1845 and 1847. 



OLIVINE. 



Olivine being very abundant in the old lavas of Vesuvius 98 

 (especially in the leucite-ophyrs of the Sornma) in the Arso of 

 Ischia, in the eruption of 1301, mixed with glassy felspar, 

 brown mica, green augite and magnetic iron, in the volcanoes 

 of the Eifel which emit lava-streams (for example, in the 

 Mosenberge westward of Manderscheid), 99 and in the south- 

 eastern portion of TenerifTe in the lava-eruption of Guimar 

 in the year 1704, I have also searched for it very diligently, 

 but in vain, in the trachytes of the volcanoes of Mexico, 

 New Granada and Quito. Our Berlin collections contain 

 sixty-eight specimens of trachyte of the four volcanoes, Tun- 

 gurahua, Antisana, Chimborazo and Pichincha alone, 48 of 



)s The recent lavas of Vesuvius contain neither olivine, nor glassy 

 felspar ; Roth. Mon, des Vesuvs. s. 139. According to Leopold von 

 Buch, the lava-stream of the Peak of Teneriffe of 1704, described by 

 Viera and Glas, is the only one which contains olivine (Descr. des lies 

 Canaries, p. 207). The supposition that the eruption of 1704 was the 

 first which had taken place since the conquest of the Canary Islands 

 at the end of the loth Century, has been shown by me in another 

 place (Examen Critique de I'Histoire de la Geoymphie, t.iii, pp. 143 146) 

 to be erroneous. Columbus saw the eruption of fire on Teneriffe, at 

 the time of his first voyage of discovery, on the nights from the 21st to 

 the 25th August, when he went in search of Dona Beatriz de Bobadilla, 

 on the Gran Canaria. It is thus noticed in the Admiral's journal, 

 under the Rubric of " Jueves, 9 de Agosto," which contains notices up 

 to the 2d September, " Vieron salir gran fuego de la Sierra de la 

 Isla de Tenerife, que es muy alta en gran in an era," " they saw a great 

 deal of fire rising with a grand appearance out of the mountain of the 

 Island of Teneritfe, which is very high ;" Navarrete, Col. de los Viayes 

 de los Espanoles, t. i, p. 5. The lady above named must not be 

 confounded with Dona Beatriz Henriquez of Cordova, the mother of 

 his illegitimate son, the learned Don Fernando Colon, the historian of 

 his father, whose pregnancy in the year 1488 so materially contributed 

 to detain Columbits in Spain, and to lead to the discovery of the New 

 World being made on account of Castille and Leon, and not for Portu- 

 gal, France, or England (see my Examen Critique, t. iii, pp. 350 

 and 367). 



99 Cosmos, see above, p. 232. 



