STOW SOITTH-APKICAN GEOIOGT. 535 



gradual lowering of the temperature of the more southern parts of 

 this coast since the limestone was deposited. 



During the formation of the sheU-banks in the Zwartkops estuary, 

 younger than the Pliocene limestone, the immense number of cer- 

 tain species of shells, which have as yet been found living only in 

 latitudes nearer the equator, point to a somewhat similar though a 

 more modified change of temperature. 



These, however, do not seem to have been the only periods when 

 this part of the world had a temperature different from that it now 

 possesses. In the Jurassic times the shells of the Trigonia-he^ in- 

 dicate a tropical or subtropical climate. 



Nor are evidences wanting that there must have been vast 

 intervening periods when the climate approached to something 

 like antarctic severity. A question worth asking is, "WTiat can 

 have been the cause of the enormous accumulations of conglomerate 

 at Enon, at the sources of the Zwartkops, at Hankey, and elsewhere ? 

 Dr. Atherstone thus writes * of this formation at Wit- water river : — 

 " the whole range of hills was actually formed of these rounded 

 pebbles ; " " the further we went the higher the cliffs became ; " 

 " a red clay formed the cement which bound them together ; " " cliffs 

 200 or 300 feet high." In the Kloofs at the sources of the Zwart- 

 kops this conglomerate is described by him as " pUed up 300 or 400 

 feet high;" at Venster - Hoek, Hankey, it is "740 feet high," 

 " composed entirelj'' of this Enon conglomerate," with a matrix of 

 " soft red sand." 



Surely this enormous accumulation of water- worn pebbles f was 

 brought about by no common action of the sea-waves and ocean- 

 tides ! but rather by the piling-up of worn fragments of rock on a 

 stormy ice-bound coast under an extreme condition of climate J. 



Configuration and origin of the Karoo Beds. — During the last 

 few years I have had several opportunities of examining portions of 

 the Katberg and Stormbei'g ranges ; and in many places they give 

 (as far as I can judge) strong evidences of having been subjected at 

 a remote period to the force of ice-action, and, indeed, that this has 

 been the great denuding agent of the Dicynodon-strata. After a 

 residence of nearly six years, the conviction has been forced upon 

 me that this denudation can be attributed to nothing else than to 

 the action of glaciers through an incalculable period of time. It 

 seems almost impossible that ordinary atmospheric agencies could 

 have eroded the surface so deeply and extensively, and carried away 

 vast tracts of strata that not only once occupied the area of the wide 

 plains and vaUeys now extending between the different branches of 



* Eastern Province Magazine, vol. i. (1857), p. 523 &c. 



f The " Enon Conglomerate " has also been noticed by Bain and Atherstone 

 as occurring in the George district, Cape of Good Hope. — T. E,. J. 



\ The suggestion of Dr. Sutherland that the great breccia-band at the base of 

 the Karoo formation in the Cape Colony and Natal is a boulder-clay of glacial 

 origin (Quart. Journ. Geol. Soc. vol. xxvi. p. 514), is consonant with this view 

 of a severe antarctic climate having again and again obtained in South Africa. — 

 T. E. J. 



