414 Transactions. — Geology. 



EXPLANATION OF PLATES XLIX.-L. 



Plate XLIX. 



Micro-photographs. 



Pig. 1 represents a feldspar crystal with three sets of twin bands. The 

 third appears as fine lines parallel to length of crystal. The altered 

 parts are in the middle. (Crossed nicols. Magnified 25 diameters.) 



Fig 2. is an instance of a crystal with a kernel of earlier formation. The 

 inside is twinned faintly^ and the twin bands die out at its edge. 

 One small x^art is twinned on the pericliue type, but very indistinctly. 

 The dark lines parallel to the corners represent an outward wave of 

 extinction. There is a row of alteration products just outside the 

 kernel. (Crossed nicols. Magnified 25 diameters.) 



Plate XLIXa. 



Fig. 3 is another crystal showing zonal structure. The inside is twinned, 

 while the outside shows several waves of extinction moving outwards, 

 but getting straighter in outline, till the form is idiomorphic. There 

 is a zone of alteration just outside the core. The twin band is con- 

 fined to the interior. (Crossed nicols. Magnified 30 diameters.) 



Fig. 4 represents a twinned augite crystal. One of the bands is faulted. 

 The fine parallel lines represent perfect cleavage. A large white 

 crystal near the edge of the field is a crystal of feldspar greatly 

 altered. (Crossed nicols. Magnified 25 diameters.) 



Plate L. 

 Map of Dyer's Pass Road. 



Art. XLVIII. — Geology of Nelson.-'' 

 By W. F. WoBLEY. 



[Read before the Nelson Philosophical Society, 12th June, 1S93.] 

 I AM only about to attempt the barest outline of the geology of 

 this district, and in doing so must acknowledge my indebted- 

 ness to the Geological Eeports, issued by the Geological De- 

 partment, and to the " Outline of New Zealand Geology," 

 prepared by Sir James Hector, Director of the Geological De- 

 partment. 



To describe the geology of Nelson it will be necessary to 

 say a few words about the geology of New Zealand as a whole. 

 New Zealand, there are good reasons for believing, is but the 

 remains of what was once an extensive continent. Soundings 

 made by the " Challenger," on her famous expedition, brought 

 to light the fact that a submerged plateau extends for many 

 miles to the eastward of New Zealand. The depth of water 

 over this plateau varies from 300 to 600 fathoms, while the 

 water of the ocean beyond the plateau has a depth of 2,000 to 



* The maps and diagrams referred to in this paper were enlargements 

 of geological map and sections issued with " Outline of New Zealand 

 Geology." 



