128 BEPORT— 1891. 



occurrence ; and even in European countries, e.g., Great Britain,, 

 it has as yet only been identitiecl in a typical phonolite forming 

 the Wolf Eock, near the Land's End/'' In Australasia it is, 

 to my knowledge, only known from a single locality — viz., 

 Phillip Island, Bass Strait, Victoria, where it occurs in an 

 older basalt celebrated for its richness in finely crystallized 

 zeolites, especially analcime and natrolite. 



Regarding this apparent scarcity of nepheline-bearing rocks 

 in these southern lands, I was therefore much gratified in dis- 

 covering the mineral about two years ago in an interesting 

 rock occurring on the Peninsula at Portobello, about twelve 

 miles east of Dunedin, and shortly afterwards in a rock of 

 identical character much nearer the city. Since then I have 

 recognised nepheline as a more or less essential constituent in 

 samples of rocks from a number of places close to and in the 

 neighbourhood of Dunedin, the examinations thereby leading 

 to the discovery of some of the rocks being typical phonolite, 

 and, in fact, of most belonging to the iilionolite cjroxiv of rocks. 

 But, regarding these examinations, I have here to record my 

 great obligations to Mr. A. Purdie, M.x\., a student of the 

 Dunedin University School of Mines, who with the greatest 

 zeal made excursions into the high mountainous parts of the 

 district, collected rock-samples, and prepared a large number 

 of thin sections for microscopic examination. Having thus a 

 great variety of nepheline-bearing rock types to choose from 

 for special description, I thought it advisable to select for this 

 purpose the two types structurally the most different from each 

 other — namel}^ one the most coarsely porphyritic (the one 

 first discovered), the other the most dense or homogeneous- 

 looking ; and in illustration of my notes I have prepared by 

 camera seven drawings of thin sections, as seen under the 

 microscope in ordinary light — five with a magnifying power of 

 '26 diameters, one of 15 diameters, and one of 120 diameters. 

 x\s a complement to this are given short descriptions of a 

 number of sections of nepheline-bearing rocks from differeiit 

 localities, for showing their mutual relations and variations, as 

 well as their respective alliances to some of the other kinds of 

 volcanic rocks occuring in the district. 



The Coaksely-porphyhitic Rock. 



The following are the main facts of the discovery of this 

 type of rock at its two places of occurrence : The existence of 

 gold in a peculiar propylite-like rock at the head of Hooper's 

 Inlet, near Portobello, induced Mr. A. Porterfield, a farmer in 

 the neighbourhood, to prospect about the district with the 

 object of discovering similar gold-bearing rock. Whilst engaged 



* J. J. H. Teall's " British Petrography," p. 367. 



