Conspicuous among the trees, for its gigantic size, and bark coloured exactly like Egyptian syenite, is the burly Baobab.  It often makes the other trees of the forest look like mere bushes in comparison.  A hollow one, already mentioned, is 74 feet in circumference, another was 84, and some have been found on the West Coast which measure 100 feet.  The lofty range of Kebrabasa, consisting chiefly of conical hills, covered with scraggy trees, crosses the Zambesi, and confines it within a narrow, rough, and rocky dell of about a quarter of a mile in breadth; over this, which may be called the flood-bed of the river, large masses of rock are huddled in indescribable confusion.  The drawing, for the use of which, and of others, our thanks are due to Lord Russell, conveys but a faint idea of the scene, inasmuch as the hills which confine the river do not appear in the sketch.  The chief rock is syenite, some portions of which have a beautiful blue tinge like lapis lazuli diffused through them; others are grey.  Blocks of granite also abound, of a pinkish tinge; and these with metamorphic rocks, contorted, twisted, and thrown into every conceivable position, afford a picture of dislocation or unconformability which would gladden a geological lecturer’s heart; but at high flood this rough channel is all smoothed over, and it then conforms well with the river below it, which is half a mile wide.  In the dry season the stream runs at the bottom of a narrow and deep groove, whose sides are polished and fluted by the boiling action of the water in flood, like the rims of ancient Eastern wells by the draw-ropes.  The breadth of the groove is often not more than from forty to sixty yards, and it has some sharp turnings, double channels, and little cataracts in it.  As we steamed up, the masts of the “Ma Robert,” though some thirty feet high, did not reach the level of the flood-channel above, and the man in the chains sung out, “No bottom at ten fathoms.”  Huge pot-holes, as large as draw-wells, had been worn in the sides, and were so deep that in some instances, when protected from the sun by overhanging boulders, the water in them was quite cool.  Some of these holes had been worn right through, and only the side next the rock remained; while the sides of the groove of the flood-channel were polished as smooth as if they had gone through the granite-mills of Aberdeen.  The pressure of the water must be enormous to produce this polish.  It had wedged round pebbles into chinks and crannies of the rocks so firmly that, though they looked quite loose, they could not be moved except with a hammer.  The mighty power of the water here seen gave us an idea of what is going on in thousands of cataracts in the world.  All the information we had been able to obtain from our Portuguese friends amounted to this, that some three or four detached rocks jutted out of the river in Kebrabasa, which, though dangerous to the cumbersome native canoes,