Basalt and of Lava from Etna. 9,1 



100.93 

 From this result we obtain the following formula :— 



9' ) 



Na3 V Si + 2 AISi + 3H.» 



K^' j 

 The gelatinizing portion is zeolitic according to its chemical 

 composition, but does not agree with any known zeolite ; it ap- 

 proaches most nearly to the Thompsonite, the formula of which 

 is probably — 



f^l Vsi + 3A1 Si + 6H, 

 Ca * J 



but which exhibits a different proportion of the alumina to the 



lime and soda, and also a different quantity of water. It may 



also be regarded as a zoisite containing water, and in which a 



part of the lime is replaced by soda and potash. 



The non-gelatinizing portion contains — 



100.97 



This analysis shews the composition of the augite ; but a for- 

 mula cannot easily be deduced from it, and in this respect it 

 agrees perfectly with the results obtained by Kudernatsch. f The 

 examination confirms in another way what was apparent to the 

 unaided eye. 



By calculating the composition of basalt from the first and 

 second analyses, we obtain the following result : — 



" In each of the two formula given in this page, the A and the H ought 

 to have additional lines drawn through their centres, but we find that our 

 types do not admit of this. 



t Poggendorff^s Annalen, voL xxxvii. p. 577- 



