654 F. Chapman — The Oiifant Klip from Natal, etc. 



The microscopic structure of the inner portion of this Ladysmith 

 specimen is seen to be both minutely and coarsely crumpled ; whilst 

 at short intervals the rock is traversed in various directions by 

 small and interrupted faults. The weathering has brought out 

 this structure of the internal portion very distinctly ; and therefore 

 the harder parts, with more silica in their composition, stand in 

 higli relief. 



The forces which have produced the structures of ' rippling,' 

 shearing, thrusting, and faulting in the central part of the mass 

 have resulted in the formation of coarser vertical faults in the 

 stronger and moi'e homogeneous siliceous layer which now, probably 

 through the folding process, forms the outer crust, 



III. — A specimen from one of the blocks found in the Ecca Shale 

 at Bester's Farm behind Waggon Hill, four miles from Ladysmith. 

 This is a dark-grey rock, weathering on the dull side to a light- 

 brown crust, along which harder bands of quartz stand out in 

 strong relief. These hard bands are thin and almost papery in 

 structure ; and they are not continuous now, but nipped and dis- 

 connected by the oblique lines of the dynamical compression to 

 which they have been subjected. The remnants of the siliceous 

 bands are thus converted into a string of small lenticles. 



The microscopic characters are like those of another specimen 

 (from Ladysmith) above mentioned ; that is, a contorted and 

 mylonized siliceous limestone with much limonite. 



IV. Note on a specimen of the Oiifant Klip of the Zydenhurg 

 District, from the Collection of Nicol Brown, Esq., F.G.S. — This 

 specimen shows strong indications of bedding lines, some of which, 

 in consequence of their being siliceous, stand out in rugged relief. 

 The rock also shows lines of faulting in a V-shaped manner (trough- 

 faults). The surface of the limestone is coarsely hollowed or pitted 

 (like elephant hide), and is of a dull bluish colour. Cold acid has 

 no effect on the rock. 



In section this rock is seen to be a dolomitic limestone. The 

 main mass is composed of tesseras of dolomite crystals with a few 

 idiomorphic ones ; that is, with their faces developed, especially 

 in the clear parts of the section. 



Darker patches in the rock, moi'e finely crystalline to granular 

 in structure, seem to point to former organic inclusions. 



V. Note on Oiifant Klip from the SterJfontein Caves near 

 Johannesburg, in the Transvaal, in Mr. Nicol Brown's Collection. — 

 (1) A greenish or slate-coloured argillaceous limestone rock. 

 Decomposing externally into a brown ochreous crust. Under the 

 microscope this specimen shows itself to be much crushed, rapidly 

 on the way to become a micaceous calc-schist. Minute quartz-grains 

 interspersed through the section. Much limonitic material present. 

 The apparent lamination seen on the fractured surface is probably 

 due to cleavage. 



(2) A sub-translucent, pale grey rock with oolitic structure. 

 Composition, a dolomite. Under the microscope the larger pro- 

 portion of this rock is seen to consist of minute rhombohedra of 



