The Volcanoes of Ciriqualand East. 105 



Bekker's house is on a large volcano, since the soil around is parti- 

 cularly poor and sour, but just at this point it seems to be rich ; at 

 any rate trees flourish on it. The form of the hills around also leads, 

 one to suspect a volcano as they form a steep-sided amphitheatre, on 

 the south of which two small pipes make their appearance. South 

 of Makomereng also there are three volcanoes in a line at right 

 angles to the general trend, and these lie right away from the 

 mountains, and are separated from them by the deep valley of the 

 Kenigha. At Ongeluk's Nek, the place over which Adam Kok came 

 with all his waggons from Griqualand West, and where he smashed 

 most of them up, there is a very large volcanic pipe partly filled 

 in with agglomerate and partly with dolerite, which is in continuity 

 w^ith a heavy flow of that material in a south-easterly direction. 

 The volcano is beautifully dissected by a tributary of the Mabele 

 Eiver, and a new road has been cut right through it, so that very 

 perfect sections in a fresh state are available for study. On the 

 west side of the volcano there is a bed of agglomerate wedged in 

 between the sandstones, showing that the shower of ashes spread 

 over the country far and wide. The particular spot was probably a 

 lake, and when the agglomerate had been deposited the ordinary 

 sedimentation followed and covered the agglomerate with sand. 

 This is the only instance of such a bed that I found in Matatiele, but 

 Dunn states that they are common round Jamestown and Molteno. 



The amygdaloidal lavas at Ongeluk's Nek contain very large 

 amygdules of quartz, calcite, and zeolites, and many of the flows, 

 have covered up soil and sediment that formed in previous flows. 

 The soil now presents a crumbly, earthy appearance, and the sedi- 

 ments, formed either along the sides of the runnels that carried away 

 the storm-water of the volcano, or in temporary lakes caused by the 

 damming up of such runnels by cross flows of lavas, have been 

 baked and hardened to such an extent that some of the shaly beds 

 have been actually porcellanised. One bed is particularly interesting, 

 showing that the greatest change is not along the sides of the bed, 

 where it was in contact with the molten lava, but in the centre. 

 This porcellanised shale was thought to be gold quartz, and it, and 

 the larger amygdules were actively prospected not long ago, but 

 wdth no results, though gold is reported to have been found in minute 

 quantities. 



At the bottom of the Ongeluk's Nek pass the amygdaloids descend 

 to the level of the plain, so that they are much more available for 

 study than at other places where they are high up on the mountain- 

 side ; beautiful examples are here afforded of ropy surface, and of 

 sections showing the lavas tilling in the inequalities on the surface 



