ON THE CRYSTALS IN LAVAS. 137 



instant of its fusion ; yet we here find a multitude of crys- 

 tals, that issued from the cratei' ready formed. Can these 

 have been produced by a first cooling of the lava-? The 

 tenorraous mass of this lava, that issued from the foot of 

 the cone, contains itself a prodigious quantity of these 

 schoerls : all their edges are distinguishable on the surface 

 of the fractures. 

 , This sanje lava, and the jets of its explosions, exhibit Another fact 



another interestino; fact. It includes, beside the pyroxene [^^P^cting this 



^ . . lava. 



schoerls, a multitude of small crystalline lamias of a 



whitish colour, that have no regular form, and appear to 



be scales from some substance splintered by the heat. These 



laminae are found detached likewise, mingled with the 



schoerls and little scoriae. Can we discover here that play 



of affinities, to which the formation of the crystals included 



in lava is ascribed, since here is no regular form .'* Besides, Cannot arise 



the play of affinities can take place only when the mole- ^'°"y^^^<^^^°^ 



cules, on which they act, are at liberty to unite, which they 



cannot be, except in a mass perfectly fluid : and this is not 



ihe state of lara, in which it is asserted to occur. They 



are in fusion, no doubt ; but it is a dull, heavy fusion, that 



has no progressive motion but on steep descents, or from 



the successive impulses given by the matter that issues from 



the volcano, and pushes before it, while at the same time 



it spreads at the sides, that which preceded it. How can 



affinities be exerted in such a mass : 



The burninar matters thrown up by the explosions of the ,, , , 



'^^ 1 / Matters t.hrov.-n 



crater, some ot which are drops of compact lava, others up by the ex- 

 fragments torn from the mass in fusion, contain likewise P'o'^'O"-^ con- 



, . tain pr loxenes 



pyroxene schoerls, which snow themselves entu'e, when 



these fragments have been exposed to the corrosive action 

 of the vapours of the crater. This action is sometimes car- 

 ried so far, as to reduce these fragments to a degree of soft- 

 ness little less than that of dough : and the schoerls there 

 being in perfect preservation, they are well distinguished 

 by their black colour on the yellow sulphurous tint of this 

 paste, which acquires some consistency in drying, but is 

 easily broken. I have collected several pieces in these dif- 

 ferent states, which are now before me. We cannot sup- 

 pose, that there was a moment of first cooling in this case: 



since 



I 



