1854.] RUBIDGE — GOLD IN SOUTH AFRICA. 3 



are rare and of extremely limited extent. The only alteration I 

 have observed in the structure and chemical composition of the strata 

 adjacent to a dyke is a little increase of hardness, and numerous 

 vertical fissures, giving the rock an appearance of being cut up into 

 cubical masses. The dykes cut each other in all directions, so that 

 we have been unable to refer them to any system or systems as to 

 age or direction. They form the central masses of the mountain- 

 ranges, which are crowned with precipitous escarpments of the igneous 

 rocks ; the sloping sides of the mountains being due to the unequal 

 wearing of the horizontal strata (see fig. 1). With the exception of 



Fig- 1 • — Diagram of the Structure of the Mountains of Stratified 

 Rock capped with Basalt, ^c. in Southern Africa, 



iron, which is abundant in both the igneous and aqueous rocks, and 

 manganese, we have not yet found in the Colony any metal in this 

 formation. 



On my arrival at Smithfield, I found the formation to be the 

 " Dicynodon strata" just spoken of, still horizontally disposed, and 

 with no traces of metamorphic action ; fossils, both animal and vege- 

 table, being found quite uninjured at 3 or 4 feet distance from even the 

 larger dykes. The stratified rocks were a hard, greenish-white, com- 

 pact sandstone (becoming brown on exposure), forming good build- 

 ing-stone, and in layers 10 or 15 feet thick, alternating with other 

 layers of nearly the same thickness, of a bluish-brown and much 

 more perishable sandstone, which is common in the whole extent of 

 the formation. Where concretions of hard blue limestone are found 

 in this rock, it is generally fossiliferous ; these concretions or nodules 

 seeming to be connected in some way with the fossil bones of the 

 Dicynodon, which are often imbedded in them. I did not see any 

 fossils in the harder sandstone on this spot, though some very like it 

 contained vegetable impressions in other places. 



The plain, or rather the broad shallow valley, in which the gold 

 was found was bounded on either side by a low range of hills ; the 

 small brook escaping to the south by a gorge in hills of 1000 or 1200 

 feet in height. (See fig. 2, p. 4.) 



The first spot I examined was the hole where the gold was first 

 found in the quartz turned up by a jackal, (A) in the sketch-plan. 

 There were a number of the usual rounded masses of igneous rock 

 lying about in apparent confusion, which, on close examination, I 

 found to result from the disintegration of two dykes which formed a 

 junction just at the spot selected by the jackal for his domicile, at A 



B 2 



