388 Transactions. — Geology. 



of New Zealand, the rocks in the neighbourhood of Lyell are 

 shown as fohated schists and granite belonging to the oldest 

 rock-systems of New Zealand, and forming part of a con- 

 tinuous band of those rocks extending from Separation Point 

 down to and beyond the Teremakau Eiver. Mr. A. McKay, 

 however, in his report on the Eeefton district, '•= mentions inci- 

 dentally that the rocks seen in the gorge of the Buller at and 

 above Lyell are schistose rocks of unknown age, the principal 

 part of which he believes to be Silurian, " although it is more 

 than possible that much younger rocks are present." I was 

 therefore surprised, when I visited that district in January, 

 1887, to find it formed of sandstones and slates similar to those 

 which have for several years been considered as belonging to 

 the Maitai system, largely injected with granite, which has 

 altered the slates for some distance into cornubianite, but 

 without any foliated schists at all. In fact, so far as I could 

 see, the Buller Eiver nowhere, from its source to its mouth, 

 runs through true foliated schists, but only through these 

 slates and sandstones pierced by granite, or through still 

 younger sedimentary rocks. This discovery makes a gi'eat 

 change in our ideas of the geology of this part of New Zea- 

 land, for it destroys the supposed continuity between the 

 foliated schists of Westland and those of Nelson. 



To enter into more detail : Both sides of the valley of the 

 Lyell Eiver are composed of sandstones and silky slates like 

 those of Eeefton, and it is in these rocks that the United 

 Alpine Gold-mine is situated. Boulders of granite are found 

 in the river-bed, but I did not see it in position. Neither did 

 I see the large block of Cretaceo-tertiary rocks shown in the 

 Geological Survey map (1886) on the left bank of the river. A 

 little below the bridge on the Nelson and Eeefton Eoad a well- 

 marked dyke of granite, 2ft. to 3^ft. thick, crosses the Lyell. 

 It can be seen in the cuttings on both sides of the river, tra- 

 versing slates and sandstones. At the south-eastern end of 

 the town there is a large mass of granite, and between here 

 and the first creek on the Nelson Eoad — a distance of about 

 a mile and a half — seven bands of altered slate alternate 

 with granite (see cut), the third slate-band from Lyell con- 



S.E. 



Section on the road east of Lyell. Distance about one and a half 

 miles, a. Granite, b. Cornubianite. 



tainiug a dyke of granite 2fc. thick. Beyond the first creek 

 we again find granite, then altered slate, and again granite 



* "Reports of Geological Explorations," 1882, p. 101. 



