Vol. 67.] WORCESTER, ROBERTSON, AND ASHTON (CAPE COLONY). 709 



(6) Upper division: the slaty series.. — The rocks of this 

 series are notably liner in texture than those just described, and 

 appear to have been deposited in deeper water ; but they are on 

 the whole of very similar character, and the transition from the 

 gritty to the shaly type is gradual. The lower part of this series 

 is well seen along the Hex-River road, on the farm Meirings Berg, 

 and also in the neighbourhood of Brewels Kloof ; while the upper 

 part is excellently exposed on the low hills immediately north of 

 the town of Worcester. 



In this division, the dominant lithological type is a fine-textured 

 silvery-grey or olive-green rock, which has been variously described 

 as slate, schist, and phyllite. Cleavage and schistosity are con- 

 spicuous, while strain-slip cleavage, both microscopic and on a large 

 scale, is very common. When weathered, these rocks take on a 

 greenish-yellow or brownish tinge, and shatter very readily under 

 the influence of weathering agents. 



A. microscopic examination of specimens of these rocks reveals a 

 structure and mineralogical composition very like that previously 

 described in the more gritty division, but of course on a smaller 

 scale. In most of the specimens from this division felspar is 

 fairly abundant in small rounded grains, and it is sometimes dis- 

 cernible also in the line cement. The principal coloured mineral 

 is olive-brown biotite, which is sometimes converted into chlorite. 

 In these specimens also the quartz-grains show incipient meta- 

 morphism, indicated by reaction with the ground-mass. Certain 

 beds have some resemblance to volcanic ashes, owing to the 

 presence of broken crystals of felspar and much micaceous 

 material. 



In a deep sluit to the west of the flag-quarry, and north-west of 

 the marble- quarry, there is a small exposure of conglomerate in 

 the Malmesbury Series. This rock is highly schistose in character, 

 with augen-struktur, and consists of scattered pebbles embedded 

 in a well-foliated silvery phyllite, which is a good deal weathered 

 and stained by iron-oxide. The pebbles, which are not relatively 

 abundant, vary from half an inch to 5 inches in diameter, but the 

 larger ones are rare; they are for the most part oval in form, and 

 evidently waterworn. They consist of vein-quartz and quartzite, 

 and do not exhibit any special characteristics. They are chiefly of 

 interest as showing the former existence of sedimentary rocks older 

 than the Malmesbury Series. 



(c) The calcareous rocks.— The limestone-bands found in 

 the quarry north of Worcester show a great deal of variation, 

 apparently due to different degrees of metamorphism, depending on 

 their proximity or otherwise to the invading tongues of granite. 

 The rocks are here much disturbed, and the relations of the different 

 types of limestone are difficult to make out. In one part of the 

 quarry there is a considerable mass of white crystalline marble, and 

 on the other side are some remarkably contorted bands of a black 

 limestone which does not seem to be much altered : this is only 

 a few inches thick. 



