chap. yii. Superficial Calcareous Deposit, 1 6 1 



East Indian islands. At the Cape of Good Hope, at 

 the base of the mountains formed of granite and capped 

 with sandstone, the ground is everywhere coated either 

 by a fine-grained, rubbly, ochraceous mass, like that at 

 King George's Sound, or by a coarser sandstone with 

 fragments of quartz, and rendered hard and heavy by 

 an abundance of the hydrate of iron, which presents, 

 when freshlv broken, a metallic lustre. Both these 

 varieties have a very irregular texture, including spaces 

 either rounded or angular, full of loose sand; from 

 this cause the surface is always honey-combed. The 

 oxide of iron is most abundant on the edges of the 

 cavities, where alone it affords a metallic fracture. In 

 these formations, as well as in many true sedimentary 

 deposits, it is evident that iron tends to become aggre- 

 gated, either in the form of a shell, or of a network. 

 The origin of these superficial beds, though sufficiently 

 obscure, seems to be due to alluvial action on detritus 

 abounding with iron. 



Superficial calcareous deposit. — A calcareous de- 

 posit on the summit of Bald Head, containing branched 

 bodies, supposed by some authors to have been corals, has 

 been celebrated by the descriptions of many distinguished 

 voyagers. 1 It folds round and conceals irregular hum- 

 mocks of granite, at the height of 600 feet above the 

 level of the sea. It varies much in thickness ; where 

 stratified, the beds are often inclined at high angles, 

 even as much as at 30 degrees, and they dip in all 

 directions. These beds are sometimes crossed by 

 oblique and even-sided laminse. The deposit consists 

 either of a fine, white, calcareous powder, in which not 

 a trace of structure can be discovered, or of exceedingly 

 minute, rounded grains, of brown, yellowish, and pur- 



I visited this hill, in company with Captain FitzRoy, and we 

 came to a similar conclusion regarding these branching bodies. 



