278 THE GAP DYKES 



across the Kei into Cathcart (see Fig. 22). From a 

 certain point on the road between the Kei bridge and 

 Toleni, not far from the Eagle's Nest, a fine view can 

 be obtained along the valleys weathered out along the 

 course of the dykes ; on the west a long line of valleys 

 with low cols between each pair can be seen on either 

 side of the Kei, and to the east a similar line of valleys 

 stretches for many miles between slightly higher ground. 



The dykes are made of a rather coarse rock composed 

 of augite, hornblende, red mica, plagioclase, orthoclase 

 (in micropegmatite) and quartz, with ilmenite, apatite 

 and zircon as accessories. The rock can be called an 

 augite-mica-diorite. 



The coarse diorite weathers more readily than either 

 the sedimentary rocks or the dolerite through which it 

 passes, consequently the minor streams in its neighbour- 

 hood have worked their way along it rather than through 

 the more resistant rocks, with the result that a series 

 of valleys with low cols between each pair have been 

 formed. These are called "gap-valleys" 1 from the 

 local name of " Transkei Gap " given to the whole series 

 of valleys by the early surveyors and residents in the 

 Transkei. 



There are two of these gap-dykes in Kentani, lying 

 parallel and about a rnile apart, but they cross, or join 

 and separate, in the N'Debe Valley. The northern dyke 

 is not continuous on the surface between the Gentuli 

 River and Cat's Pass, but the separate parts are very 

 probably connected underground. The longest valley 



1 The gap-valleys of the Transkei have been described in detail in the 

 T. S. A. P. S., vol. xiv., p. 66, 1903. 



