186 Mr. Bain on the Geology of Southern Africa. ' 



nearly parallel to the coast. There can be no doubt that its former horizontal 

 extent was much greater than at present, for we find detached masses of it to the 

 south of Governor's Kop and Zuurberg (see Sections No. 3 and 2), and in the Cold 

 Bokkeveld (see Section No. 1), having, according to my idea, covered all those im- 

 mense mountain-masses before the period of their upheaval. I have no doubt also 

 that many detached portions will be found to the south of the Great Swartberg 

 chain ; but my acquaintance with that part of the country is too limited to enable 

 me to point them out. 



In what manner could this extensive mass of igneous matter have been poured 

 out on the surface of the earth, whose northern limit perhaps extends thousands 

 of miles in the interior, and whose eastern termination must for ever remiain a 

 mystery? In vain have I searched for dj'kes, as the channels of eruption, such as 

 are so plainly visible in the other trap-rocks of the country. It is true, that at its 

 junction with the carboniferous schists in Albany the strata are frequently vertical, 

 and even overlie the porphyry, and are much altered by heat (see Catalogue of 

 Rocks of Section No. 3, specimen No. 14, marked A in the section), giving the 

 latter the appearance of being the upheaving rocks. At Ecca Valley, however 

 (marked B in Section No. 3), at Pluto's Vale, and at Hantam, the opposite 

 extreme, the reptiliferous beds rest conformably on the igneous rock, and no indi- 

 cations of heat are exhibited by those slates (as the specimens in the collection will 

 show), the porphyry having evidently cooled before the deposition of the former; 

 consequently this great zone of igneous rock cannot be an immense dyke, as might 

 otherwise be. supposed. 



From' the numerous imbedded pebbles of granite, sandstone, quartz, and clay- 

 slate, apparently not altered by heat, one might be led to believe that the whole 

 was an aqueous deposit ; but after inspecting the magnificent amorphous masses of 

 hundreds of feet in height, as seen at Pluto's Vale in Albany, Toverberg in the 

 Western Karoo, and at KUp Rug in Hantam, with many other splendid sections, 

 where not the smallest sign of stratification appears, that idea also falls to the ground. 



In this dilemma, I trust, I may not be considered visionary if I attribute the 

 whole to the production of an immense volcano, which we may suppose to have 

 existed somewhere near the junction of the Vaal and Orange Rivers, or perhaps 

 about the site of the present Compass Berg, whose peak rises to the height of 

 10,000 feet above the sea-level ; and thence deluged with fiery billows the Silurian (?) 

 plains, and spread ruin and desolation over the carboniferous forests for tens of 

 thousands of square miles. 



Besides the imbedded pebbles, &c., above mentioned, I found at one place, near 

 Zout Kloof in the Karoo, a great number of rounded calcareous nodules imbedded 

 in this rock, from 3 inches to a foot in diameter, some of them being perfectly 



