310 Ohservathns upon the 



of salts or s-nlphur by sublimation, and never any crystal of 

 a solid matter, such as those coiilained in lava. 



In order to found this opinion he fixes upon two epochs : 

 the first took place, according to him, in the crater itself, 

 upon the occasion of a forn}er cooling; and the second epoch 

 took place outside the lava itself. A former cooling in the 

 crater! Supposing we should admit this supposition. Here 

 is a lava cooled and hardened. But in a lava which has at- 

 tained this state, not one of the bodies it contains can be 

 any longer separated from it in an isolated manner ; for this 

 purpose it would be necessary to replunge it into the fire of 

 the volcano, or perhaps it would not enter into fusion. 



The crystals which are found isolated upon the cone of 

 the craters have been separated in the very bosom of the 

 volcano by the boiling which the lava in fusion undergoes, 

 and the squirtings of its explosions. The crater opened 

 upon ^tna in I669 shows a very instructing example of 

 this. The very large cone elevated by this orifice is covered 

 with an innumerable multitude of pyroxene schorls, all of 

 them, without exception, covered with a slight crust of the 

 lava which contained them mixed among the scoriae which 

 contained the latter themselves. This lava, from the first 

 moment of its fusion, could not have been cooled for a single 

 moment, yet here there arc a multitude of crystals issued 

 from the crater ready formed : Is it possible they could have 

 been so formed by a former coding of the lava? The enor- 

 mous mass of this lava which has issued from the foot of 

 the cone contains itself a prodigious quantity of these 

 schorls, all the traces of ihem are distinguished upon the 

 surface of the fractures. 



This same lava, and {he jets of its explosions, present an- 

 other interesting fact. It contains, besides the pyroxene 

 cchorls, a mulfitude of small crystalline flakes of a whitish 

 colour, which have aio regular form, and seem to be nothing 

 else than the shining particles of a substance, which are pro- 

 duced by the heat. These flakes are also isolated, mixed 

 with schorls and small scorite. Can we here discover the 

 play of affinities to which is attributed the formation of the 



crystals 



