248 OJ' THE CRYSTALS IN LATAS. 



SO distinct, would have a stronger resemblance of wood than 

 this, were it not for its glassy lustre. I have another piece, 

 vitreous likewise, one of the surfaces of which, that was 

 exterior, is marked with a multitude of very small threads, 

 arranged in some places in undulations resembling the woody 

 fibres round a knot. ^ 



This the case From these examples I am led to believe, that the spe- 

 with the sup- pjjj^gjj from tlig. Isle of Bourbon is wholly lava, with a woody 

 posed piece of p-,> ^ ^ 



palm, appearance on one of its faces ; for at all events a vegeta- 



ble, even in the state of wood, could leave nothing after 

 its combustion, which must be inevitable, but a vacuity 

 in the lava, and traces of charcoal; and by no means the 

 impression of woody fibres, still less tjie fi;bres themselves^ 



In support of his principal opinion Mr. Fl. de Bellevue 

 adduces several arguments, which I shall pass over, because 

 our business is with facts, not conjectures. One of theiu 

 Grand erup- is the following. *' The great volumes of lava, that act 

 tjon^ ow like ^j^^ principal part in volcanic eruptions, burst out from the 

 crater, from the sides of the mountain, or from its base. 

 They proceed with rapidity from the very focus of the vol- 

 cano, possessing an incomparably greater degree of heat 

 than the matter that rests in the crater. This heat, this 

 rapidity, cause them to spout forth and flow like water, and 

 therefore the cannot permit any crystals to form in them. All that are 

 crystals form- found in it afterward are produced during its repose and 

 ied in it while f • \^- it ' 



cooling. refrigeration. 



Tlowing like I must first remark, that these expressions frequently re- 



water a meta- peated, that lava spouts out and flows like water, are merely 



pression. metaphorical ; for lava, far from flowing like water under 



any circumstances, leaves in succession, by hardening, ajl 



its matter on the ground it flows over. 



Eruption of Mr. Fl. de Bellevue did not recollect the lava of Etna of 



Etna of 1669, 1669, which I have already mentioned. This lava, issuing 



from the base of that great volcano, traversed a space of 



ten miles in length, and advanced into the sea, where jt 



accumulated in prodigious heaps, after having covered its 



route with its matters to a vast extent in breadth and thicl^- 



jiess. This certainly was to be reckoned among the lavas, 



that act the principal part in volcanic eruptions. Now thjs 



Java, of which I have pieces before my eyes, I again assert 



