Nature . , the Zambesi within its gorge sinks somewhatmore rapidly in the same direction, so that while imme-diately below the Victoria Falls the river is barely 400 feetbelow the lip of the gorge, this is increased to about 500feet at the Songwe, to about 600 feet at the Tshimamba,and to 800 feet at the place some 35 miles farther eastwhich we reached from the south bank. Aneroid observ-ations showed a difference of more than 900 feet betweenthe level of the river at the foot of the Falls and WankiesDrift, which represents the descent of the water in passingthrough the Batoka Gorge ; and unti
Nature . , the Zambesi within its gorge sinks somewhatmore rapidly in the same direction, so that while imme-diately below the Victoria Falls the river is barely 400 feetbelow the lip of the gorge, this is increased to about 500feet at the Songwe, to about 600 feet at the Tshimamba,and to 800 feet at the place some 35 miles farther eastwhich we reached from the south bank. Aneroid observ-ations showed a difference of more than 900 feet betweenthe level of the river at the foot of the Falls and WankiesDrift, which represents the descent of the water in passingthrough the Batoka Gorge ; and until this steep gradientis very much reduced the Zambesi must continue to deepenits channel along the easiest lines before there is time forit to straighten out the angularities of its course. The results attained by this selective erosion arestrikingly exemplified in the immediate surroundings of theVictoria Falls. The wonderful Chasm, in places onlv80 yards wide, into which the broad river is here precipi-. From a photograph hy Mr. F. W. i.—The Gorge immediately below the Tshimamba Cataract. Thedepth of the canon here is about 600 feet. The Zambesi, in the fore-ground, is confined in a channel from 20 to 25 yards wide. Note howthe strong jointing of the b isalt governs the course of the river andtends to produce zigzags in the low-water channel. tated, owes its chief features to the presence of an eastand west vein, probably a fault-plane, that cuts vertical!}through the basalts. This vein, which I found to be wellexposed in the steep Recess or gully at the eastern end ofthe Chasm, is partly filled with calcite and other soft vein-stuff, and the rock adjacent to it is shattered and readilydecomposed. When the falls, in receding northward, struckupon this vein, they readily hollowed out a transversetrench across the whole breadth of the river, from whichthe waters escape southward through a single narrowchannel. But, having passed this easy place, it is be-coming inc
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