552 F. Chapman — The Olifant Klip from Natal, etc. 



the Ecca Beds, with central mass and concentric coatings similar 

 to the others already mentioned. 



The occurrence of these peculiar blocks in large numbers, at 

 places so far apart, points to some extensive physical operations 

 under which their formation and deposition have taken place. 



Mr. Fred. Chapman suggests that these blocks, with a more or 

 less concentric structure, have been due to sigmoidal folds in crushed 

 Palaeozoic rocks. Their distribution was probably due to ice-action 

 during the formation of the Ecca Shales. 



The encrusted blocks and their association with the Ecca Shale 

 are precisely the same in the four several localities in which I have 

 now found them. 



There can be no question about their being travelled blocks. 

 I have been over the whole country within a radius of 15 miles 

 round here, and have failed to find anything approaching the kind 

 of stone of which the central portion consists. Therefore I am 

 certain that I have not met with the rock from which these blocks 

 were derived, nor, as far as I am aware, is there any previous mention 

 of the occurrence in Natal of what I must perforce call ' dolomite,' 

 such as the central mass of these encrusted blocks, which is a blue 

 magnesian limestone, effervescing on application of a mineral acid. 



[If the Ecca Beds are really extra-morainic deposits in connection 

 with the Dwyka Conglomerate, it may be to the latter we have to 

 look for the immediate source of the blocks, and to far-away southern 

 regions for the earlier rocks from which they originally came. — 

 T. E. J.] 



V. — Notes on the Olifant Klip from Natal, the Teansvaal, 



AND LydENBURG. 



By Frederick Chapman, A.L.S., F.R.M.S. 



(Appendix to Dr. Exton's paper on the Travelled Blocks in the Ecca Shales near 



Ladysmith.) 



I. — Specimen from one of the blocks lying on the Ecca Shale 

 on the declivity near the Klip Eiver at the Station Hospital, 

 Ladysmith. This is a bluish-grey rock of close texture, with 

 a flaky and sometimes conchoidal fracture. The broken surface 

 does not reveal the rock's internal structure ; but on the weathered 

 surface, which appears as a brown crust, the siliceous strings and 

 bands passing through the rock stand out in high relief. The 

 surface effervesces freely when touched with acid. 



Under the microscope this rock appears to be a mylonized 

 siliceous limestone. It was perhaps originally a calcareous sand- 

 stone ; possibly having organic remains (as shell-fragments), more 

 or less massive. 



The arenaceous part of the rock now appears as brecciated fragments 

 of sandstone, alternating with contorted and fibrous calcareous 

 material. The whole structure shows an extraordinary amount 

 of crushing, and exhibits various stages in the formation of 

 a cleaved rock. The harder arenaceous portion occurs as strings 

 of rifted quartzose fragments, once continuous, but now broken 



