228 THE VOLCANIC NECKS 



several in Aliwal North, while a few w^ere incidentally 

 noticed in Basutoland and in the Orange Kiver Colony. 



In none of these vents is the crater form still pre- 

 served, for in every case, the necks have been laid bare 

 by denudation. They are thus differently situated with 

 regard to the surrounding beds according to the amount 

 of denudation to which the latter have been subjected. 

 Some of the necks, as in Barkly East, are still surrounded 

 by volcanic beds, but the majority are in contact with 

 the Cave sandstone or else with the lower subdivisions 

 of the Stormberg series. 



The necks are distributed over a wide, and so far as 

 can be judged, fairly well-defined area or belt. The 

 southern limit of this area is a line drawn through 

 Sterkstroom, Indwe, Xuka and onwards towards Natal 

 at a short distance from the foot of the Drakensberg 

 escarpment. The northern boundary is not well known, 

 but it is probably near a line drawn from Steynsburg 

 through Aliwal North and Zastron. The existence of 

 several volcanic vents in Basutoland 1 has been recorded, 

 but with these exceptions the distribution of the pipes 

 outside Cape Colony is quite unknown. 



The pipes within the area just defined are distributed 

 in a most irregular manner, usually in little groups, 

 while sometimes three or more lie arranged along a 

 straight line. Such an absence of definite or orderly 

 arrangement is paralleled by the Carboniferous volcanoes 

 of Central Scotland, the Permian vents of Fifeshire, those 

 of the Eifel, the Swabian Alps and the Auvergne. 



In regard to size .and shape the necks show great 



1 S. S. Dornan, G. M. t p. 113, 1908. 



