194 Transactions of the South African Philosophical Society. 



there are outcrops of Dwyka conglomerate separated by an interval 

 of 60 feet of swampy ground from the next outcrop to the south, 

 which is a breccia of quartzite fragments, angular and sub-angular, 

 set in a matrix with much calcite. This rock crops out for some 

 30 yards, when there is nothing else seen till one meets with the red 

 Enon conglomerate dipping at an angle of 45° to S. 30 E. on the 

 right bank of the river on Coerney farm. I was uncertain of the 

 nature of this calcitic breccia until I found a very similar rock in 

 close association with the tuffs, breccia, and lava of Duncairn and 

 Mimosa. 



Following up the fault line eastwards from Coerney Eiver the 

 lava is again seen about a mile from the river on the ridge to the 

 north of a side valley descending westwards from Mimosa." The 

 width of the band of lava rapidly swells to some 1,000 yards, and 

 this is maintained, or increased, as far as the main valley descending 

 from the Nieuw Post escarpment through Mimosa, where the width 

 is reduced to about 700 yards, but it again swells near the Duncairn 

 boundary. The most easterly trace of the lava and tuffs I could find 

 are on Duncairn, where they terminate bluntly towards the east 

 without any apparent gradual reduction in width. The termination 

 takes place on the divide between the valley in which Mr. Eeed's 

 boreholes are situated and the next kloof to the east. East of this I 

 found a thickness of some 20 feet of quartzitic breccia between the 

 Enon conglomerate and the Witteberg quartzites, and at one place, 

 just east of the road to Waggwa, the transition from this breccia to 

 the solid unbroken quartzite can be followed inch by inch in a dis- 

 tance of about 30 yards. In the above-mentioned valley descending 

 from Mimosa to Coerney Eiver and on the hill north of it there is 

 some red tuff amongst the lava, but this part of the fissure is mainly 

 filled with lava ; in the northernmost head kloof of this valley, 

 which almost reaches the Nieuw Post escarpment, a great body of 

 tuff and breccia is met with. This mass of fragmental rock is quite 

 1,000 yards wide from north to south, and on the north it is probably 

 in contact with the Witteberg quartzites, cutting out the Dwyka 

 conglomerate and perhaps the Lower Dwyka shales, which were 

 found both to the west and east. The shape of the tuff and breccia 

 mass cannot be determined on account of the soil and bush, but it is 

 probably a true volcanic neck in the form of an enlargement of the 

 fissure we have been tracing. The Nieuw Post escarpment is a very 



* The farm Mimosa, belonging to Mr. Walton, is not marked as such on the 

 latest Divisional Map of Alexandria. It includes the farm called Thornleigh on 

 that map and a part of Gorah (V. F. 7, 6), but I do not know its boundaries.. 

 Mimosa Station is on it. 



