62 EXPERIMENTS on il'III NSTO NE and LAVJ, 



which furround Mount iEtna. The fituation of this mafs is 

 fingular : It refts upon a little hill, formed of loofe fcoria, the 

 fummit and fides of which are covered by the ftony mafs, fo 

 that no crater is vihble. It {truck me on feeing it, and I found 

 M. Dolomieu had formed the fame opinion, that the lava had 

 rifen up in a perpendicular direction, and had flowed over on 

 all fides. Its great thicknefs, and fmall extent, feem to favour 

 a conjecture which this naturalift has formed with regard to 

 feveral lavas, that they were erupted at the bottom of an ocean 

 which once covered Sicily, and, being quickly cooled by the 

 contact of water, had been prevented from flowing far. The 

 conjecture fqems plaufible enough * ; and, having no proof that 

 this fubftance made part of an external current, as I have with 

 refpect to the firft two mentioned, I do not exhibit it as a lava 

 with the fame confidence. Whatever be its hiftory, however, 

 it poffefTes the chemical properties common to whin and lavas. 

 Its glafs yielded a dark grey cryltallite of uniform texture. 

 Befide it in the drawer, now on the table, I have placed a cry- 

 ftallite, formed from the whin No. i. which refembles it in 

 every refpect. 



No. 4. Lava of Iceland. 



I received the fpecimen from a perfon who found it on the 

 fpot ; but not being acquainted with the circumftances of its 

 original pofition, I cannot be certain that it is a lava. It has 

 however every appearance of being fuch. 



It is a blue homogeneous fubftance, having fome chryfolites 

 fcattered irregularly through it. Nearly half its bulk is occu- 

 pied 



* M. Dolomieu afcribes the formation of part of Mount iEtna itft-lf to a fimilar 

 caufe. I fhall have occafion, in another part of this paper, to confider that opi- 

 nion- 



