72 Transactions of tlie South African Philosopliical Society. 



towards the middle of the Kabakazi that a perfect view is obtained ; 

 standing on one of the foothills in this neighbourhood one can look 

 right down the Gap for some ten miles, the last seven being occupied 

 by the Kogha, and the last four of these containing the tidal estuary 

 of that river. The tidal portion presents in miniature the appear- 

 ance of the Beagle Channel ; the height of the cliffs is here from 700 

 to 800 feet ; the northern cliffs are densely wooded and the slope is- 

 so steep that each tree stands clear of those below it. The pre- 

 vailing tints of these forests are dark olive and grey-green, and from 

 the glossy masses of foliage lit up only for a short while in the 

 middle of the day, one hears the hoarse bark of the Lory or the 

 heartrending wails of the baby-bird. At the bottom of the Gap 

 where a small ledge of rock protrudes, dew remains all day long, 

 and the surface is slippery with sodden mosses. On the south side 

 there are few trees, and those mostly Mimosas ; the surface of the 

 ground is covered with thick soil, on which rank long grass thrives. 



The walls of the Gap consist principally of Karroo shales and 

 sandstones, but in the southern Gap about Nxaxo these include a 

 thin sheet of dolerite, double in places, which the Gap-rock apparentl}^ 

 has not had much difficulty in piercing. East of the Manubi road by 

 Lusizi, however, a thicker sheet comes in, which is probably an inde- 

 pendent sheet above the one we have distinguished as the Manubi 

 Sheet. It caps the plateau in isolated patches near the junction 

 of the Kabakazi and the Kogha, and both the northern and southern 

 portions of the Gap have here evidently pierced it. At the actual 

 junction of the Kabakazi with the Kogha, the dolerite is seen rising 

 from the bed of the river as a thick massive sheet, which eventually 

 rises to the level of the plateau, and constitutes the Manubi sheet. At 

 the junction of the Quaninga Biver with the Kogha, this sheet has 

 already become a capping sheet, the lower walls of the Gap-valley 

 being formed of sandstone and shale. At this place, also, the 

 outcrop of the Manubi sheet turns south-west owing to the plateau 

 being cut away by the coastal streams, and the rest of the course of 

 the Gap-valley to the sea is between walls of sedimentary rocks. 

 The actual mouth of the Kogha is turned south and away from the 

 Gap-valley, the Gap-rock crossing over to the Willowvale side of the 

 river, and running out to sea over a low nek between a small south- 

 ward promontory and the mainland. 



Between Gqunqi and the Kabakazi there is an outcrop of a 

 peculiar rock running in a north and south direction ; it is dis- 

 tinctly more acid than the Gap-rock and might be called a fine- 

 grained granite or a granophyre. There are important differences- 

 l)etween it and the Crap-i-ock, but its occurrence as a straight dyke, 



