jfChtmleatAnalyfis of Three Species ofWhinJhnei and Two of Lava. 439 



ANALYSIS IVw- 



Lava of Catania, ^tna. 



This lava, and the fpecles to be next mentioned, were brought from Mount .^tna by 

 Sir James Hall and Dr. James Home. At their requeft I analyzed fpecimens of each,. 

 Mineralogifts are well acquainted with thefe lavas, from the defcriptions which have been 

 given of them by M. Dolomieu ; therefore it is unneceflary for me to mention their exter^ 

 nal chara£lers. 



The lava of Catania gives- »■ powder of a light grey colour, which is very little changed 

 in appearance by being heated red hot. After it is wet, it becomes dark grey. When 

 this lava is reduced to fmall fragments, fome parts of it are attradled by the magnet, and 

 others are not. In fine powder it is but feebly attra(Sled ;, and after ignition its q.ualities in; 

 this refpect do not feem to be altered. It foftens at 33 of Wedgwood. The fpecific gra- 

 vity of the pieces moft free from air bubbles, is 2.79;. 



I have expofed this lava, in the manner already defcribed, to various degrees of heat, 

 from rcdnefs to 158 of Wedgwood, and conftantly obferved that it never loft the fmallelt. 

 ■ weight.: 



When boiled like the whins la muriatic acid, the part remaining undiflblved weighed 

 6Z per cent. 



There are in 100 parts,^ 



Silex, - _ - » _ ^i 



Argil, - - - - . - - 19 



Oxydeofiron, - .. — — . 14,50 



Lime, - - - - - . 95° 



Soda, about r- - - - - 4 



Muriatic acid, about- — - - "!• i 



99. 



ANALYSIS V: 



Lava S" Vettere, Piedimonte, uStna *.' 



This fpecies gives, like the preceding, a greyifli powder, which becomes dark grey 

 when wet, and its colour is fcarcely affe£lcd by being expofed to a low red heat. It is 

 but feebly attradled by the magnet, whether in fmall fragments or in powder ; and its 

 qualities in this refpe£l are not changed by low ignition, 



• Dolomieu, in defcribijig this lava, fays, that its frafture is conchoidal, tike that of ftlex. Tlie'fjteci- 

 men which I analyzed had an uneven frafturcj and its colour was blatkifli-blue ; in other refpefts, how- 

 ever, it anfwercd toDolomieu's defcription, 



lit 



