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the delta so formed tlie channels of the rivers are all advancing into the lakes. 

 This progress is necessarily very slow, from the great depth which has to be 

 filled up. But the amount of matter so deposited is conclusive evidence of the 

 many ages during which the present geographical order of river and lake must 

 have existed. This silting action has gone on principally at the northern ends 

 of the lakes, where invariably a large river enters. The lakes have each in 

 this way been filled up for several miles. The smaller rivers which enter at 

 the sides of the lakes are also encroaching. Thus the Dingle has formed its 

 delta more than half way across the original breadth of Hawea Lake. The 

 continuation of the process, together with the deposits of the Hunter River, 

 will, in time, reclaim several miles of the lake. 



The lessening of the lake areas is also promoted by the eroding action of 

 the rivers issuing from them. The high terraces surrounding them show that 

 their surfaces must have been considerably higher at one time. A minor 

 triangulation has been extended over the middle and upper part of Lake 

 Wakatipu. It determines that the terraces at Greenstone, White Point, and 

 Frankton, are each 100 feet above the present level of the lake. There are 

 other terraces, the heights of which have not yet been ascertained. In the 

 accurate determination of the heights of terraces above the present lake level, 

 there is, apart from finding the ancient lake levels, the means of detecting any 

 secular variation of level that may have taken place in the island since the 

 lake system began. If, for instance, the west side of the island is sinking and 

 the east side rising, the old contour marks or terraces of the lake will not be 

 parallel to its present surface. The detection of this difierence, supposing the 

 variation to have taken place, would no doubt be a delicate operation if the 

 oscillation has been insignificant. If, on the other hand, the oscillation has 

 been considerable, it could not fail of detection.* There are several other 

 questions concerning Lake Wakatipu which the extension of the trigono- 

 metrical survey will throw light upon ; there is the abandoned river bed at 

 Kingston, and there is the supposed leakage of part of the lake waters through 

 the Kingston Moraine to the Mataura Eiver. 



From the twofold influence of silting up and erosion, it is plain that the 

 tendency is to transform each lake into a valley, with a river running through 

 it. This pi'ocess has been already completed on a small scale in some of the 

 higher valleys. A moraine has, in the first place, dammed across the valley, 

 and then the lakes so formed have been silted up, and are now a succession of 

 flats, with a river running through them, and rushing over the moraines as a 

 rapid. In the higher valleys there are also, in some places, masses of rock 

 lying confusedly across the valley, that at first sight appear to be moraines, but 



* The terraces are due to alterations in the level of the outfall of the lake, and 

 could not be affected by such oscillation. — Ed. 



