120 ON EROSIONS OF THE EARTH'S SURFACE. 



miles east and west. The Ghaut mountains lie near the western coast, rising from 

 2000 to 7000 feet, with high table lands stretching away from their east side. 

 This region is penetrated by numerous valleys, sometimes 600, 800, or even 

 1000 feet deep, whose precipitous sides exhibit numerous alternations of compact, 

 amygdaloidal, and tufaceous trap, capped by laterite and red clay, in layers appa- 

 rently horizontal. The same layers appear on both sides of the valleys undis- 

 turbed; showing, beyond question, that the depressions have been the work of 

 erosion rather than of internal upheaving forces. These valleys are numerous, 

 especially along the western face of the Ghauts, and the eye can often take in a 

 distance of 10 to 15 miles; the layers of trap showing continuous stripes all the 

 way; nay, much further, if the observer travels along the valley. 



These are certainly striking examples of erosion by streams, in a country where 

 we cannot suppose ice to have aided the work. But tropical rains are very power- 

 ful. I am indebted for these facts to Rev. Ebenezer Burgess, missionary at Satara, 

 in southern India, and who was formerly a resident for years at Ahmednugger, 

 which lies in the same great trap region. To him, also, I am indebted for the facts 

 stated in the next example. He visited Table Mountain, on his return recently, 

 and obtained specimens of the different rocks composing it. 



11. Table Mountain, at the Cape of Good Hope, in Southern Africa. — This is a 

 vast mass of horizontal strata of sandstone, some 600 or 800 feet thick, superim- 

 posed upon granite and older inclined sandstone and metamorphic slate. The 

 height of the mountain is stated at 3800 feet; which makes it visible 30 to 40 

 miles at sea. That this outlier of sandstone, capping Table mountain, must once 

 have had a wide extent, no geologist will doubt, nor can it be reasonably ques- 

 tioned that it has been brought into its present shape by the action of the ocean, 

 when this was at a higher level, or the mountain at a lower level. The slate and 

 lower sandstone, that are inclined at a large angle, must have been tilted up by a 

 force beneath, or acting laterally. But if the mountain has been raised since the 

 deposition of the horizontal sandstone, it must have been a secular elevation, bring- 

 ing up the continent bodily and equably. 



12. Table lands and intervening Valleys in the vicinity of Natal, in South Africa. — 

 Accident has put into my hands two sketches of the scenery in that region, with a 

 description, from the pencil and pen of Mrs. Lydia B. Grout, wife of Rev. Mr. 

 Grout, American missionary among the Zulus; and these are too appropriate to 

 the object of this paper, and too well executed to be lost. I therefore have taken 

 the liberty to append these drawings (Plate XI. figs. 1 and 2), and copy the 

 accompanying descriptions, from a letter written by Mrs. Grout. 



A glance at these drawings will satisfy the geologist that they represent a region 

 analogous to Cape Town, and this makes it probable that these table lands are very 

 extensive in Southern Africa, since Natal is some 800 miles north of the Cape. 

 And we see enough in the drawing and description to satisfy any one that the 

 erosions in Southern Africa have been on the same great scale as on other conti- 

 nents. 



"The scene," says Mrs. Grout, "which it (Plate XI. fig. 2) portrays, is about three 



