Olservations on Volcanoes and thslr Lava. 2G3 



lent, and muddy. When we reflect, indeed, that these 

 crystals, the schorls of volcanoes, and leucitc;, are found in 

 such great number in their paste, all insulated, and without 

 bearing anv marks of adhesion to any rock ; when we con- 

 sider also, that these schorls are found insulated one by one 

 in myriads, mixed with the small scoriae, thrown up by 

 the mouths which vomited forth the enormous lava of 

 jEtna in ld(39; that this lava itself is filled with it, — it is not 

 easy to conceive how they could all be contained in a solid 

 rock. It is still more difficult to conceive that tires capable 

 of fusing granite, horn rock, and porphyry, should spare 

 schorls, leucites, and some other substances, which are 

 fused and reduced to glass in our furnaces. 



The volcanic mountain of \"iterl)o exhibits lavas where 

 the leucites are so near each other that they occupy 

 between them more space than the paste of the lava which 

 contains them. 



The lava of ^tna contains, besides schorls and some 

 olivins, a nuiltitude of crystalline laminis, whitish, and 

 semi-transparent. They are named without hesitation 

 J'eld-spur, which appears to me not so certain as is sup- 

 posed. 



These laminae are two or three lines in breadth, and 

 about half a line in thickneso. They are found also sepa- 

 rated from each other, mixed with the schorls and the 

 email 'scorice of Mount Rosso, or the crater of 1669. In 

 the bed of a rivulet which runs dov/n from Mount ^tna I 

 found rolled fragments of old very black lava, which contained 

 some of these laminae in as great quantity as any marble can 

 contain fragments of shells, it would be very extraordi- 

 nary if these laminae proceeded from feld-spars, such as 

 those with which we are acquainted, and that thev should 

 not be found mixed with any fragment larger or better de- 

 termined, which might indicate in a certain manner that 

 origin. 



Admitting the hypothesis, that the strata from which the 

 lavas proceed are in a pulverulent and nniddy state, con- 

 taining elements of all these small crystals, one may con- 

 ceive how they are formed there, insulated, grouped, or 

 solitary, and are found then in the lava in that state of in- 

 sulation. 



The fragments of natural rocks thrown up by Vesuvius 

 are not of the same kind as the matters of which the lava 

 is composed. Most of these fragments arc micaceous 

 rocks, with laminae of greater or less size, and of a kind of 

 granite called ik'nifc, I have found some composed of 



white 



