5° 



92 CHEMICAL ANALYSIS 

 One hundred parts contain, 



Silex, - 



Argil, - 18.50 



Oxyd of iron, - - _ 16.75 



Carbonate of lime, 3 



Moifture, and other vol. matter, - 5 



Soda, about - - 4 



Muriatic acid, about - 1 



98.25 



ANALYSIS IV. 



Lava of Catania, JEtna. 



This lava, and the fpecies to be next mentioned, were brought 

 from Mount iEtna 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 unnecefTary for me to mention their external characters. 



The lava of Catania gives a 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 attracted by the 

 magnet, and others are not. In fine powder it is but feebly at- 

 tracted ; and after ignition its qualities in this refpecl: do not 

 feem to be altered. It foftens at $5 of Wedgwood. The fpe- 

 cihx gravity of the pieces moft free from air bubbles, is 2.795. 



I have expofed this lava, in the manner already defcribed, 

 to various degrees of heat, from rednefs to 158 of Wedgwood, 

 and constantly obferved that it never loft the fmalleft weight. 



Wher 



