THE KARROO SYSTEM 233 



in the Drakensberg and in Basutoland, the scarcity of 

 intercalations and the absence of more normal agglom- 

 erates from the necks is certainly remarkable, because 

 the great volcanoes of the present day consist chiefly 

 of f ragmen tal tuffs which thin out quickly in all direc- 

 tions, though they may cover wide areas. 



From the existence of now widely distant outliers of 

 lavas apparently of Stormberg age in the Transvaal, 

 Portuguese East Africa and Rhodesia, it is clear that 

 this formation must have at one time covered an enor- 

 mous tract of country. Whether these northern lavas 

 issued from necks or from fissures is unknown, but it is 

 not unlikely that there was here a parallel to the exten- 

 sive flows of the Deccan area of India and of Idaho in 

 North America, in both of which volcanic necks appear 

 to have played a very subordinate part. The Drakens- 

 berg type of volcanism may possibly, therefore, have 

 been intermediate in nature between the normal erup- 

 tions of the present day and those that produced the 

 lavas of the Deccan and of the Western States of 

 America. 



The part played by the volcanic episode in the geolo- 

 gical history of the country can be more conveniently 

 dealt with in chapter xiii., where its relation to previous 

 and subsequent events will be explained. 



5. THE CORRELATION OF THE KARROO SYSTEM. 



The correlation of the various members of the Karroo 

 system with foreign beds is attended by many difficulties, 

 due chiefly to the fact that the Karroo beds were not 



