The Marble Beds of Natal. 515 



The camera re-ts on a divided horizontal circle, which can he 

 adjusted to a truly horizontal position hy levelling-screws. There 

 is a tripod stand and head, with suitable appliances for supporting 

 and adjusting the instrument in position. The camera is provided 

 with a rectilinear doublet lens and iris diaphragm and rack-and- 

 pinion focussing adjustment. It is made of aluminium, and it is 

 surmounted by a telescope adjustable in altitude and fitted with 

 vertical and horizontal webs ; and it is also surmounted by a 

 revolvable tubular level. 



The details of construction and the peculiar features and adjust- 

 ments of the instrument are fully described in the paper, and some 

 of the chief purposes to which it may be applied in furtherance of 

 geological research are pointed out. The maker of the instrument 

 is J. J. Hicks, of 8 Hatton Garden. 



4. ' The Marble Beds of Natal.' By David Draper, Esq., E.G.S. 



A ' crystalline limestone of enormous thickness ' was mentioned 

 by Mr. C. L. Griesbach, in 1871 (Q. J. G. S. vol. xxvii. p. 56), as 

 occurring along the lower course of the Umzimkulu, in the county 

 of Alfred, in the southern part of Natal. Since the time of his 

 visit there the country has been opened out by settlers, and some 

 attempts have been made to utilize this marble. The chief 

 mass of this rock is met with at about 7 miles inland, in the 

 Indwendwa hill-range, within the fork formed by the junction of 

 the Umzimkulu and the Umzimkulana, over 700 feet above sea- 

 level, and continuous with the tableland westward. This consists 

 of granite, overlain by the massive marble, roughly stratified, 

 which is denuded north and south of the hill into the gorges of the 

 two rivers, and is continued on the opposite flanks until cut off by 

 faults. The north fault divides it from the Table-mountain Sand- 

 stone lying on clay-slate : and the south fault divides the granite 

 from the Table-mountain Sandstone and clay-slate. The bedding 

 of the marble dips towards the rivers, on each of their flanks, and 

 strikes E. and W. 



In quality the marble varies from coarse to fine-grained, and in 

 colour from pure white to deep red. The coarse-grained variety 

 contains 5 to 13 per cent, of carbonate of magnesia. Calcareous 

 tufa, in some places several feet thick, has been formed from the 

 marble. 



From the junction of the two rivers eastward, slate is seen below 

 Table-mountain Sandstone ; and on the latter is a long stretch of 

 the Dwyka Conglomerate to the coast, greatly disturbed for the 

 most part, and pierced by two dolerite-dykes, between which a 

 patch of Ecca Shales is preserved. 



The author concludes that the marble was deposited on the 

 granite, and probably on the Malmesbury Slates near by, before they 

 were disturbed ; that it does not extend far under the neighbouring 

 hills ; and that some of its local detritus indicates that the riv ers 

 ran at higher levels within relatively recent times. 



