362 . Geology of 



consisting of "boulders, shingle, gravel, sand, and loam (silt), where 

 the precious metal has been retained which has been brought down 

 from the ranges. For an enormous lapse of time these ranges have- 

 been subjected, first to marine and afterwards to subaerial denudation.. 

 Thus, where this lower gold-drift has been preserved, which, owing to 

 its peculiarly loose character, could only happen under very favourable 

 circumstances, it is obvious that the precious metal contained in it 

 must be abundant. To this conclusion we must arrive, if we con- 

 sider that during the gradual rise of the land, great denudation of 

 the rocky surfaces of the Island went on continually, in which the 

 gigantic glaciers took a considerable share, and that the rivers becoming 

 larger were able to destroy not only greater masses of rocks, either by 

 undermining their banks and rolling boulders of greater size along, but 

 also by carrying the gold derived from the destruction of those sources 

 farther with them towards the sea. As soon as rivers of any size 

 reached the rather shallow sea, deltas of large dimensions were 

 formed, where the gold was ultimately deposited. 



In mv Eeport on the formation of the Canterbury plains, I have 

 shown how such fanlike beds are formed, and how they are liable to 

 be destroved, or to be covered by fluviatile deposits of more recent 

 origin. That also the marine young miocene or older pliocene beds, 

 immediately underlying the great gold-drift, underwent considerable 

 denudation in many localities, is well exhibited by ranges consisting 

 of these rocks, situated from four to eight miles from the coast line, 

 and 600 to 800 feet high, falling steeply in many places towards the 

 east. Thev oftt-n form true razorback ridges, running parallel with 

 the direction of the central chain. Remains of the great gold-drift 

 are still preserved on the summit of these ridges, thus showing that 

 these older alluvial beds, in many instances assuming the texture of a 

 conglomerate of considerable hardness, covered uniformly the whole 

 zone, and that since their deposition remarkable denudation has there 

 taken place. In this older alluvium the principal goldfields of TVest- 

 land are situated, of which the Greenstone, Kumara, "Waiinea, 

 Kanieri, and Ross diggings are the most important. It is especially 

 in those localities that favourable circumstances have existed for a 

 preservation of these deposits. If we examine these beds with care, 

 and follow them a considerable distance, we find that they consist 

 mainly of the alluvial deposits of a large river, coming from the 

 north-east through the present Grey valley, skirting the western 

 foot of the Hohonu range where the Greenstone diggings are situated. 

 This river was joined by several tributaries as far south as the Totara 



