GEOLOGY. 251 



cause precipitation of vapour, when abundant, is rendered 

 matter of ocular demonstration in that very striking 

 phenomenon so common at the Cape of Good Hope, where 

 the south or south-easterly wind which sweeps over the 

 Southern Ocean, impinging on the long range of rocks 

 which terminate in the Table Mountain, is thrown up by 

 them, makes a clean sweep over the flat table-land which 

 forms the summit of that mountain (about 3850 feet high), 

 and thence plunges down with the violence of a cataract, 

 clinging close to the mural precipices that form a kind of 

 background to Capetown, which it fills with dust and 

 uproar. A perfectly cloudless sky meanwhile prevails 

 over the town, the sea, and the level country, but the 

 mountain is covered with a dense white cloud, reaching to 

 no great height above its summit, and quite level, which, 

 though evidently swept along by the wind, and hurried 

 furiously over the edge of the precipice, dissolves and 

 completely disappears on a definite level, suggesting the 

 idea (whence it derives its name) of a " Table-Cloth." Occa- 

 sionally, when the wind is very violent, a ripple is formed 

 on the serial current, which, by a sort of rebound in the 

 hollow of the amphitheatre in which Capetown stands, is 

 again thrown up, just over the edge of the sea, vertically 

 over the jetty where we have stood for hours watching a 

 small white cloud in the zenith, a few acres in extent, in 

 violent internal agitation (from the hurricanes of wind 

 blowing through it), yet immovable as if fixed by some 

 spell, the material ever changing, the form and aspect 

 unvarying. The " Table-Cloth " is formed also at the com- 

 mencement of a "north-wester," but its fringes then 

 descend on the opposite side of the mountain, which is no 

 less precipitous/ 



Other illustrations, perhaps more pertinent, are supplied 

 by sand ripples on the shore, and by the contour of sand 

 drifts, while an illustration of reboundings out at sea, 

 like to the serial rebound described in the passage cited 

 from the writings of Sir John Herschel, are supplied by 

 banks in some of the Argyleshire lochs, which, vertical to 



