Thomson. — Glacial Action in Otago. 



317 



At intermediate 



points < 



rise 4,978 ; from whence the following comparison was made, with actual 

 survey data : — 



By Ellipse. By Survey. Differences. 



At source ... ... 0000 ... 0000 ... 000 



3548 ... 3934 ... 386 



4390 ... 4541 ... 151 



At exit to sea ... 4978 ... 4978 ... 000 



Again, taking the survey data of the Taieri River, we find the same 

 conformity. This was less to be expected than in the preceding rivers, as its 

 course is more than ordinarily tortuous, rising, in the Lammerlaw, at a 

 distance of only 35 miles from the sea, yet it has a total length of nearly 

 128 miles. Here again, where the country is free from rocks and mountains, 

 its bed approaches the ellipse ; where the course is obsti-ucted by hard rock and 

 precipitous hills, as in Strath Taieri, it is modified in the manner due to the 

 indicated cause. 



For the calculation of the ordinates we have : length of valley equal to 

 640,920 feet, rise 3,820 feet; from whence the following comparison was made, 

 with the data given by actual survey : — 



By Ellipse. 



At source 0000 



2476 



2993 



3523 



3776 

 At exit to sea ... 3820 



So far encouraged, I next investigated the levels of the Molyneux or 

 Clutha, using such points as had been settled by actual survey ; and here I 

 first met with apparent non-compliance with my rising convictions. The 

 properties of the Clutha appeared to difier from all other rivers yet investigated. 

 Its course was seen to cross the great valley systems of this part of New 

 Zealand, and its source would have more fairly belonged to the western slopes 

 of the great backbone of the Middle Island than to the eastern. It passes 

 through the Wanaka Lake (a painting of which is on the table, taken by me 

 on its first discovery, in December, 1857) within 26 miles of its fountain, 

 which I have placed in Mount Nix, but which might as fairly have been 

 placed in Mount Brewster on the opposite side of the valley, or in Haast's 

 Pass, at the low elevation of 1,716 feet. Leaving the Wanaka it crosses the 

 great hollow that stretches fi'om Timaru, by the Lindis, Kawarua, and Dome 

 Passes to Invercai'gill ; then it pierces the Dunstan range ; then it crosses the 

 hollow of the Manuherikia and Pomahaka ; after which, piercing the Beaumont 

 Gorge, it issues in the plains and delta near the sea. Thus, while its course 

 runs counter to prior experience, its levels are also equally divergent. It will 

 be observed that, though the divergence is more at the ordinate nearest its 



At intermediate points 



By Survey. 



Differences. 



0000 



000 



2620 



144 



2834 



159 



3165 



358 



3802 



26 



3820 



00 



