28 M. Lowe's Analyses of 



99.66 

 From this no further conclusion can be drawn ; but the pre- 

 ceding analysis proves that the basalt from Wickenstein is a 

 compound of crystallized augite with a compact zeolitic sub- 

 stance and disseminated magnetic iron-ore. Of these component 

 parts there were contained in the fragment analyzed : — 

 Augite, .... 55.58 



Zeolitic mineral, . . • 39.81 



Magnetic iron-ore, . . . 4.61 



100.00 

 The lava from Etna consists of a grey-coloui-ed basis, in which 

 are imbedded small greyish-white tabular crystals of a felspathic 

 substance, blackish-green crystals of augite, and small grains of 

 olivine. Professor G. Rose has determined this felspar-like por- 

 tion to be Labradorite, from its re-entering angle on the most 

 distinct cleavage faces, and from its being accompanied by 

 augite. * It occurs in the lava in large quantity ; the augite is 

 found more sparingly, and the olivine is still less abundant. 

 The lava is from the stream which in 1669 destroyed a great 

 part of Catania ; the portion analyzed was obtained from the 

 collection of the late Professor F. Hoffmann. 



The decomposition of this lava was accomplished in the same 

 manner as in the basalt. The gelatinized mass was to the un- 

 gelatinized as 24.89 to 75.11. Repeated experiments convinced 

 me that no loss of weight resulted from a long continued red 

 heat ; the external aspect remained unchanged. 



• Poggendorff's Annalen, vol. xxxiv. p. 29. Von Buch and Elie de Beau- 

 mont are also of opinion that the felspathic component part of this lava is 

 Labradorite, vol. xxxvii. p. 18n. 



