CHAP. II. GEOLOGY OF KEBRABASA. 37 



others, our thanks are due to Lord Eussell, 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 

 Eobert," 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 oould 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 cata- 



