The Rev. S. Ilaughton's Notes on Mineralogy. 223 



degree of metaniorphism the lava has undergone subsequent to 

 its emission. On reducing the insoluble parts of the preceding 

 lavas to percentages, we find — 



Insoluble portion of Dunedin Lava. 





No. 1. 



No. 2. 



Silica 



5372 



5537 



Titanic acid .... 



1-78 



1-34 



Alumina 



14-24 



1510 



Peroxide of iron . 



3-46 



3-51 



Protoxide of iron . . 



4-37 



1-93 



Protoxide of manganese. 



0-26 



0-27 



Lime 



8-74 



13-56 



Magnesia 



4-46 



5-10 



Soda 



6-05 



300 



Potash 



0-87 



1-47 



Loss or gain .... 



+ 2-05 



-0-65 



100-00 100-00 



This seems to be a mixture of Labradorite and Augue, and is 

 very constant in the two specimens examined. 



No. XVI. On the Chemical Composition of four Zeolites, pre- 

 sented by Colonel Montgomery to the Geological Museum of 

 Trinity College, Dublin. 



Some months ago. Colonel Montgomery presented to the 

 Geological Museum of Trinity College some fine specimens of 

 Zeolites found by him in the Bombay Presidency, four of which 

 seemed to me worthy of chemical analysis and of beiug recorded. 



No. 1. Apophyllite. 

 This mineral occurs in fine clear crystals coating the foliated 

 Stilbite No. 2. 



These crystals occur in the dimetric system. 

 Its chemical analysis gave the following results : — 



Oxygen. 



^26-902 



8-175 



99-84 49476 



This analysis agrees very well with those of Apophyllite given 

 in the books, but it is very difficult to assign its rational for- 

 mula. It has been proposed to borrow as much oxygen from 



Silica . 



. 51-60 



26-791" 



Alumina 



. 0-24 



0-111 



Lime 



. 25-08 



7-130 



Magnesia 



. 008 



0031 



Soda . 



. 0-63 



0160 



Potash . 



. 5-04 



0-854- 



Water . 



. 16-20 



14-399 



Fluorine 



. 0-97 





