460 Transa ctions. — Geology. 



of orthoclase and quartz. The matrix in which they are imbedded is a 

 structureless glass, densely crowded with an immense number of very minute 

 yellowish brown granules, nearly uniform in size, and quite translucent. 

 Black grains of magnetite are also scattered through the mass. The section 

 cut contains a pale red crystal of irregular form, which exhibits no double 

 refraction — it is evidently garnet. 



Some of the orthoclase contains numerous cavities filled with brown glass, 

 and one of the quartz crystals contains a characteristic rhomboidal cavity with 

 a vacuity and five or six belonites. 



structure 



streams of microlites and brown glass bend round the larger crystals, and 



clearly indicate the plastic condition of the mass subsequently to their for- 

 mation. 



No. 353 (Snowy Peak Ha?igeJ is a rock of quite similar character. 



Art. LXXV. 



By J. C. Firth. 



»/ 



[Read before the Auckland Institute, 26th August, 1874.] 



^ Early in 1873 I commenced sinking a well in my grounds at Mount Eden, 

 with the view of obtaining a constant supply of water. I was led to undertake 

 this work from the circumstance that at various points around the mountain 

 springs of excellent water are met with. The most notable of these is the 



gallons daily of most excellent water. 



I do not know that a record of my explorations will present any features 

 of much interest to the general public. To myself, though unsuccessful in 

 my search for water, they were full of interest, for, as I penetrated each 

 successive lava stream, it seemed like the turning over of the leaves of some 

 ancient and unknown book. I am disposed to believe I have obtained a few 

 facts which may, in the hands of scientific men, be of some little use in 

 helping them to elucidate some of the phenomena which in bygone times have 

 played so great a part in changing the features of the land we live in. The 

 point of commencement was 329 feet above sea level, and 313 feet below the 

 summit of the mountain. The depth to which I penetrated was 212 feet, or 

 within 1 1 7 feet of sea level at high water mark, or about thirty feet below the 

 bottom of Mr. Seccombe's well before referred to. 



The accompanying section presents the thickness, position, and details of 

 the successive beds of volcanic ash and Uv. tw™!, ™v^ t i . 



