EXPERIMENT'S on WHINSTONE and LAVA. 61 



when expofed to a temperature of 2 2, they cryftallized rapidly, like 

 mod of the whins, into the liver cryftallite. This laft property 

 is common to all the lavas. 



No. 2. Lava of S ta Venere. 



This current has flowed in the neighbourhood of a little cha- 

 pel, called S ta Venere, above the village of Piedimonte, on the 

 north fide of Mount iEtna. Owing to the ftrong refemblance 

 which it bears to flones fuppofed not volcanic, we took care 

 that our fpecimens mould be broken from the actual current ; 

 and to one of them, though moftly compact, is attached a 

 fcorified mafs, which had made part of the external furface. 

 The folid part is of a black, or rather dark blue, colour, very 

 fine grained and homogeneous, having a multitude of minute 

 and fhining facettes vifible in the fun j in this, and in other cir- 

 cumftances, it greatly refembles the rock of Edinburgh Caftle. 

 This lava is the fecond in M. Dolomieu's Catalogue, and is well, 

 defcribed, p. 186*. 



The pure black glafs formed from this lava yielded, in the 

 regulated heat, the mofl highly cryftallized mafs we have ob- 

 tained from any lava or whin. 



No. 3. Lava of La Motta di Catania. 



This is likewife compact; and homogeneous, but for a num- 

 ber of fmall yellow grains of chryfolite fcattered through it, 

 (defcribed by M. Dolom 1 eu, p. 191 f). It has been thrown 

 up by a partial eruption burfting through the fandftone hills 



which 



*" Lave homogene noire : fon grain eft fin et ferre, il eft un peu briilant, comme 

 " micace lorfqu'on le prefente au foleil ; fa caffure nette et feche eft concheide 

 " cornme celle du filex." 



f It belorjgs to the fifth variety of his eompacl lavas, . 



