miles across an open plain, and then pass by deep narrow gorges through a barrier of greywacke which rises from 600 to 800 feet directly across their path, whereas they would have had no difficulty if they had followed along the western flank of this ridge through the open valley which stretches from Sherwood. Downs past Fairlie to the vicinity of Cave. Throughout this stretch there is no serious obstruction to the course of the stream, the only difficulty—and that a slight one—being the low downs lying just south of Fairlie and occupying nearly the whole breadth of the valley. Park thought that they were the remnants of a moraine, but I do not think they are glacial at all (1939, p. 55). Why, then, have these two rivers taken such a remarkable course? It can hardly be that the drainage is superimposed, and it is almost certain that it is antecedent, that is, the two streams maintained their old courses across the grain of the country as it was then, in spite of the rise of the barrier of greywacke across their paths. The youthful form of the groges suggests that their formation, and the uplift of the block which necessitated their cutting, took place in very recent times. The position of the Tertiary limestone near Fairlie demands that faulting took place along the line indicated, so it is merely the question of the date of this movement. This case and that of Wharekuri, both associated with areas close to the Mackenzie intermont, lend support to the thesis that the region as a whole was in an unstable condition in Late Tertiary times, and I can see no reason why the formation of the large intermont should not be assigned to Late Pliocene or even to the earliest Pleistocene times. The occurrence of coal at a height of over 4,000 feet above the sea in the angle between the Godley and Macaulay Rivers at the head of Lake Tekapo should be mentioned in this connection, although it is not possible at present to place it in its proper stratigraphical position with any degree of certainty (Speight, 1921, pp. 42–3). It may belong to the early Tertiary Coal Measures of Marwick's Wharekuri succession, and, if so, its significance as an indicator of deformation in the Late Tertiary in the Mackenzie area is not of any special value, although it seems improbable that incompetent beds like coal measures should have persisted so long in such an exposed position; this seems to be against their being of Eocene age. But if the coal belongs to the measures sometimes associated with the rusty-brown gravels, then it clearly indicates that important diastrophic movements occurred in this region at the close of Tertiary time. After the area had taken on the form of an intermont, it was modified by ice action, at first somewhat slightly—if we adopt the explanation of the origin of the cross section of the Tasman Valley near Glentanner given earlier—and then by stream action. This was followed again by much more active glacial erosion, which modified the valleys, deepening and widening them, covering their sides with a veneer of lateral moraine, and depositing diagonally across the middle of the basin the morainic complex which stretches south-west from the south-eastern corner of Lake Tekapo, past Balmoral and the Irishman's Creek to the southern end of Lake Pukaki, and after a break resuming at the southern end of Lake Ohau, and continuing