74 Transactions. 



The saddle is one of the most striking features in the whole district. 

 Viewed either from the south-west — i.e., from the Gouland Downs (see 

 tig. 8) — or from the north-east — i.e., from the Aorere Valley — it appears 

 against the sky as a perfect catenary curve four miles in length. It 

 sags from a height of about 4,000 ft. at the south-eastern end (Mount 

 Perry) and about 3,750 ft. at the north-western end (the Wakamarama 

 Range) to a height of about 2,500 ft. above sea-level in the centre. The 

 catenary form of the curve is so striking that the feature was pointed 

 out to the writer by a resident of the Aorere Valley as an indication 

 of profound glacial erosion. There can, however, be no doubt that it 

 is of tectonic origin. It is as though, during the episode of uplift, while 

 the Aorere-Gouland depression as a whole lagged behind the blocks which 

 now form the ranges to north-west and south-east, a strip here had 

 failed to break away from either side, but had sagged in the middle so 

 as to assume the true catenary form. 



The Slate Eange . 



Mention has already been made of the Slate Range subsidiary block. 

 For three miles — the full length of the block — its scarjj forms the 

 northern boundary of the Gouland Downs, while its width in a north- 

 south direction cannot exceed one-third of its length. Unfortunately, 

 a comjjlete description of this interesting little block cannot be given, 

 as the writer saw only the southern side. 



At the eastern end, as previously noted, the upper surface of the 

 Slate Range would ])ut for the ravages of erosion be continuous with 

 the higher north-eastern part of the Gouland Downs ; but on all other 

 sides the block appears to be bminded by dislocations. The scarp facing 

 the Gouland Downs has been referred to above as the " front " of the 

 range. An assumption has thus been made that the Slate Range is 

 a tilted block, and that opposite to the fault-scarp front facing south 

 there is a back slope to the north. This must be so, because the even- 

 ness of the crest-line and the small dissection of the front shoAv that in 

 the vicinity of the crest the upper surface is nearly flat and slopes back 

 so as to lead the drainage northward. A glimpse of tlie top of the 

 range caught from the sloj^e of Mount Perry confirms the above view. 

 The flat surface of the top of the range can only be a portion of the 

 dislocated denudation plain found throughout the district; and it seems 

 probable that initially the northward slope of the surface and its pro- 

 bable cover formed, with the scarp of the western Wakamarama Range, 

 a fault-angle depression determining a consequent east-v\'est reach of 

 the Big River (see fig. 3), now, no doubt, superposed on and deeply sunk 

 in the underniass. 



Tlie soutliMard-facing fault-scarp of the Slate Range, which has an 

 average height of about 700 ft., presents the usual appearance of blunt 

 spurs ending in line (see fig. 7, nnd Plate V. fig. 1). Tlie spurs and 

 the intervening steep-srade gullies are forested, with the exception of 

 one spur, which stands out as a bare and also sharp-edged facet because 

 its surface is veneered with a thick vein of quartz. Tlie quartz vein 

 evidently filled an ancient fissure which has guided the more modern 

 fault. 



The Drnlnar/e and Dii<xerfinn of the Gnulaiul Dmnix. 



The drainage of the Gouland Downs is collected in the faidt-angle 

 depression between the gently sloping " downs " surface and the scarp 



