Vol.51.] ME. D. DRAPER ON THE MARBLE BEDS OP NATAL. 53 



rugged, and covered for the most part with dense bush and long 

 grass, greatly increasing the difficulties of exploration. 



Bare rock (principally marble) lies in isolated patches in the 

 bush, and loose boulders and rock-masses are numerous under the 

 crags and in the rivers. 



IV. Geological Conditions. — From the coast inland for a distance 

 of about 5 miles, Dwyka Conglomerate, similar to that found in the 

 Cape Colony and Natal, is the prevailing rock. Petrographically it 

 presents no special features, but has evidently been greatly dis- 

 turbed, presenting undulating lines, as though it had been sub- 

 jected to pressure. Cleavage-planes are numerous up to the first 

 fault (the dyke), marked M in the section facing this page. 



Two such dykes, M, M', lying about 1 mile apart, and each 

 more than 100 yards in width, have intersected the .Dwyka Con- 

 glomerate (see fig. 1). They consist of dolerite, similar to that 

 found in connexion with the Ecca Shales and Dwyka Conglomerate 

 farther inland. 



Between the dykes, a small patch of Ecca Shale, lying a few feet 

 lower than the conglomerate on the outer side of the dykes, has 

 survived. The Dwyka Conglomerate between the dykes passes 

 gradually into Ecca Shales, and their line of junction is not defined. 



"Westward of the second dyke, M', Dwyka Conglomerate again 

 crops out, lying upon Table-mountain Sandstone, C, both dipping 

 eastward. 



The last-named formation consists principally of coarse gritty sand- 

 stone, similar to that found in the Table Mountain at Cape Town. 

 The conglomerates which generally occur in connexion with this 

 series are here represented only by thin lines of coarse grit and small 

 pebbles. 



The Table-mountain Sandstone rests upon clay-slate, of which 

 series, however, only small portions are exposed ; the principal 

 outcrop is on the eastern side of the Umzimkuluana valley, at 

 the junction of that river with the TJmzimkulu. Up as far as 

 St. Helen's Rock, a crag about 200 feet high, marked B in fig. 1, 

 the river is tidal. 



Proceeding westward, the next rock met with is granite ; and, as 

 it rises to an altitude of over 700 feet in the ridge known as the 

 Indwendwa Hill (along the sides of which the principal marble 

 masses, roughly stratified, are situated), no doubt a great fault 

 exists, which has lowered all the rocks eastward of the fault. 



The granite is grey in colour, and remarkably poor in mica ; it is 

 covered by the marble, but shows through whenever the marble has 

 been removed by atmospheric influences or erosion. The junction 

 between the marble and the rocks west of it is obscure, the 

 whole surface being covered by debris (E) from the hills. The 

 upper portion of these hills consists of Table-mountain Sandstone, 

 resting upon clay -slate. 



A small mass of marble, at * in fig. 1, detached from the main 

 body, now lies tilted to an angle of about 80°, and surrounded 



