AUCKLAND INSTITUTE.

New Zealand Herald, Volume XLII, Issue 12909, 4 July 1905, Page 3

AUCKLAND INSTITUTE.

THE WORK OF RIVERS.

A' LECTURE on "Rivers and their Work" was delivered! by Mr. B. de 0. Clarke, M.A., at the Auckland Institute last evening. There: was a crowded' attendance, and the lecture proved to be most instructive and interesting. Mr. Clarke first referred to the ' origin of rivers, showing a diagram of an idealistic new country, with the rivers, at first, running straight to the sea. He then explained the causes of erosion and the in- . fluence of velocity of rivers on the transport and laying down of material, and followed this up by demonstrating the silting up of lakes by rivers, and showing an illustration of this process in operation in the Lake Country in England, comparing it with the same thing, but on a much larger scale, going on at Lake Pearson, South Island. The formation of deep gorges by rivers was next illustrated, and a picture was shown of the Kerikeri Falls, Bay of Islands, where the river had fallen over a hard rocky bed, the fall scooping out the softer _ rook beneath the harder material overlying it which formed the upper riverbed. A picture of the Waitangi Falls was also shown, and the action going on at these falls was explained to be similar to that of Niagaraa breaking back of the land, as it were. The formation of deltas was then dealt with, reference being matte to a physiographical map of the mouths of the Ganges, and the enormous amount of material thrust out into the Bay of Bengal in "the form of the Sunderbunds. The peculiar features of the mouths of the Mississippi and also the emtio course of that river as it approached towards the sea were also fully described, together with the causes which made this great waterway so distinct from many other of the chief rivers of the globe. It was useless, Mr. Clarke held, to attempt to bank such rivers artificially, and this was emphasised by the terrible inundations which had followed the banking- of the Hwangho and the Mississippi itself. A great bend on the Tennessee River was shown, where a peninsula was formed by the loop. The isthmus of this enclosed land was ■■being fretted away, and would in time, it was stated, disappear, the river cutting its way through and banking up and enclosing the water in the loop, making it a lake. The influence of rainfall on rivers was referred to, a picture being shown of the rain-scored and rapidly-erod-ing country around Mount Tarawera. The case of hard, resistent rocks left standing as witnesses to long and powerful erosive action on the part of rivers was dealt with, and a typical soenie of the effects of such action in the western territory of North America was exhibited. Some stress was, laid upon ' the influence of vegetation ■ in the protection of the land against erosion, and several striking examples were given of the sterility that had resulted from ruthless destruction of the bush in the anthracite basin of the Appalachian Mountains. The influence of climate and earth movement, 'on the behaviour of rivers was also referred to, particularly in the case of the grand canyon of the Colorado. The Waikato and its terraces near Cambridge, as illustrating elevation of the land, and the indentations of the Bay of Islands and the Hauraki Gulf (where rivers entered them) as illustrating depression— drowned rivers—were also referred to. One problem Mr.' Clarke left with his audience for themselves to solve, viz., Whj did the Waikato, which when it left Lake Taupo going in the direction of the Bay of Plenty, turn sharply to the westward a little to the east of Atiamuri, and so continue north and westward until it emptied itself into the sea on the 'West Coast? Even near Cambridge it would seem to have bad the inclination towards the valley of the Thames; but it turned again towards the west, through the Taupiri gorges. The lecture, which although of such an important character, was delivered in the "language understanded of the people," ! and was followed with rapt attention from beginning to end. A number of beautiful slides were used in the course of' Mr. Clarke's remarks, which clearly elucidated the lesson he strove, and that with marked ! success, to impart to his audience. At the close Professor A. P. Thomas, president of the institute, conveyed a vote of thanks to the lecturer.