454 Transactions. — Geology. 



gold. Molybdenum, tungsten, tin, antimony, and arsenic are 

 also found in small quantities in many parts of the range. The 

 great quantity of iron and sulphur alone would argue a younger 

 age than that of ordinary intrusive granite. The argillaceous 

 slate through which it has burst is, as has been said, according 

 to Hector, of Devonian age, and, according to Hutton, of car- 

 boniferous ; and con-esponds in this respect with the formation 

 of Longwood, the Takitimos, Lake Te Anau, and the south of 

 Lake Wakatipu. As there are no fossils, this can only be inferred 

 from the lithological character of the strata. There is, however, 

 little room to doubt that it is at least not younger than the 

 Devonian. The outburst must, therefore, have taken place 

 posterior to this period, but probably at no great distance of 

 time, geologically speaking. 



It is probable that the basin of the Southland Plain, now 

 filled up by younger formations, was formed at the time of this 

 outburst, and that the elevation of the Bluff Eange was at the 

 expense of Southland, by the extrusion of material in a plastic 

 condition from under the surrounding district. There is evidence 

 to show that strata may become plastic at no great elevation of 

 temperature in many parts of the Hokonui District, in formations 

 ranging, according to Hector, between the Permian and the 

 Cretaceous. In many places, where there is not the least sign 

 of any volcanic agency, patches occur, often not more than an 

 acre or two in extent, of true trap rock full of small round 

 boulders, and rock of a basaltic character, which must have 

 resulted from the ordinary strata becoming plastic through 

 chemical agency, and presenting all the appearances of an 

 incipient volcano on the smallest possible scale. 



The Cannon Ball sandstone of the Bastion and the Otapiri 

 (so named by the officers of the Geological Department) seems 

 to have originated in a similar way. If this be so, it is quite 

 conceivable that the ancient strata under the Southland Plain, 

 underlying the great Silurian and Devonian period, had, from 

 chemical agencies, become plastic on a large scale, and, under 

 pressure from the slow evolution of gases, had ruptured the 

 overlying strata that imprisoned the sulphurous semi-fluid mass 

 at the weakest places — in this case, along the line of the Bluflf 

 and New Eiver Eanges— and by exuding a great viscid drop-like 

 irregular excrescence, formed, on solidifying and recombination 

 of material, the present range of granitic hills, extending from 

 Euapnke to the Now Eiver Heads. 



Whether this hypothesis will fit in with all the facts, or not, 

 must be left to the judgment of observers. It may at least serve 

 till a better is found. Between the Grcenhills quarries and the 

 Mokomoko, the slates flanking the syenite are dark-blue, and of 

 a fine compact texture, intersected here and there by veins and 

 dykes of white quartz, which, being in the vicinity of much 



