Glacial Conglomerate in the Table Mountain Series. 7 



but is dropped near the mouths of the streams. It is probable that 

 the series was deposited by a river or several rivers running over a 

 slowly subsiding area. On this supposition alone we get over the 

 difficulty of the preponderance of coarse sediment, its great thickness, 

 the occasional layers of pebbles, and the general absence of the fine- 

 grained material which must have been produced by the denudation 

 of the ancient land from which all the sand came. The fine mud 

 must have been carried away and deposited beyond the area we have 

 access to. As to the sources of the deposits it is unsafe to speculate, 

 but there are good grounds for the belief that the northern part of 

 Cape Colony was a contributor. 



It is a well-known fact that great thicknesses of gravels, sands, 

 and fine dust accumulate in desert regions, but the Table Moun- 

 tain series does not agree in many points with desert formations. 

 To take one important point, there are no deposits of soluble salts, 

 such as gypsum ana rock salt, within the group, nor have any 

 pseudomorphs or casts of crystals of these substances been found 

 in it. The presence of such deposits is characteristic of deserts, 

 and their formation on a greater or smaller scale, dependent on the 

 extent to which drainage facilities are wanting, is one of the 

 necessary results of the conditions which give rise to desert 

 regions. 



Though fiuviatile conditions will account for the bulk of the forma- 

 tion, the wide distribution of the shale band averaging two hundred 

 feet in thickness in the upper part of the series points to a change of 

 circumstances of considerable duration ; an increased rate of depres- 

 sion of the area, by which it was removed from the limits of deposi- 

 tion of coarse material, and converted into a lake, may have brought 

 about this change. It was in this lake that the mudstone forming 

 the matrix of the Pakhuis conglomerate was deposited, and into it 

 were dropped by floating ice the finely-striated boulders shaped by 

 glacial action. From the absence of angular fragments freshly 

 derived from the parent rock mass, we may suppose that the 

 boulders were carried to the places where they are now found from a 

 considerable distance ; they were probably derived not from the 

 immediate shores of the lake but from the country behind, by the 

 combined agencies of glaciers, streams, and floating ice. The area 

 over which the glacial conglomerate has been observed — less than 

 one hundred square miles are included within the lines connecting 

 the outcrops furthest removed from each ether — is so minute com- 

 pared with the whole extent of the formation, that it is as yet 

 impossible to know how far the glacial conditions affected the whole 

 area, but it is to be expected that the conglomerate, or at least 



