398 REPORT—1905. 
the folds were produced by direct tangential thrust. The direct thrust theory also 
has to explain how a force could act at a distance when the material through 
which it is transmitted is so heavy in proportion to its strength, and there is 
therefore immense friction to overcome. 
The resemblance of these Baviaan’s Kloof fold-basins to pits found between 
two sets of crossing ripple marks has suggested that certain mountain folds are 
produced by earth-shaking waves which become retarded when approaching an 
immovable buffer, such as a mass of granite anchored to the deep sub-structure of 
the earth’s crust. This theory is further illustrated experimentally by what 
happens in a lead sink where hot and cold water are let in alternately at one end 
from a tap; the disturbances produced by this gradually cause ridges to form at 
the further end of the sink, though the lead is too pliant to allow a direct thrust 
thus to act at a distance.! 
‘Schaarung’ and ‘fold are’ structure may also be explained on the wave theory, 
whereas ‘ block up-lift’ structure is rather a problem in isostasy. 
6. Report on the Fossiliferous Deposits at Kirmington, Lincolnshire. 
See Reports, p. 160. 
JOHANNESBURG. 
TUESDAY, AUGUST 29. ¢ 
After the President had delivered his Address (see p. 375) the following 
Papers were read :— 
1. The Rhodesian Banket. By Professor J. W. Grecory, /.R.S. 
The first extensive contribution to the geology of Rhodesia is in Sawyer’s 
‘Goldfields of Mashonaland,’ wherein he called attention to the existence of some 
very ancient conglomerates. These beds have recently been the subject of lively 
controversy, as they have been proved to be locally auriferous, and as they have 
been called ‘ banket.’ Protest was promptly made against their identification as 
banket on the grounds, (1) that banket is a local term which should be restricted 
to the Rand or at least to the Transvaal; (2) that the beds are not true sedimen- 
tary conglomerates, but are either crush-conglomerates (as advocated by Griffiths) 
or eruptive breccias (as maintained by von Dessauer). The author has recently 
examined the beds in the field, and found that several distinct things have been in- 
cluded in Rhodesia as banket ; among these are some crush-conglomerates and crush- 
breccias, and a diorite dyke with amphibolite segregations; but the main mass of 
the material is a sedimentary conglomerate. The sedimentary origin of this latter 
material is proved by five lines of evidence: (1) the conglomerates alternate 
with fine quartzites which are uncrushed, and sometimes show well-preserved 
current-bedding ; (2) the shape of the pebbles is that characteristic of typical 
sedimentary conglomerates, and not of crush-conglomerates or igneous breccias ; 
the pebbles are not nipped or fractured, except where the conglomerate has been 
crushed, and such cases are met with in the Rand banket; (3) the pebbles include 
a very mixed assortment of rocks: granites, diorites, granulites, quartzites, vein 
quartz, cherts, jasperoid, schists, &c.; these rocks often resemble those found 
near the banket, but they do not necessarily consist of the immediately adjacent 
country rock; (4) pebbles of different rocks have different shapes and sizes, 
suggesting that they have travelled from different distances; thus at the Hunyani 
drift the quartzites commonly occur in flat slabs, the diorites in large irregular 
boulders, the granites or grano-diorites in round spherical baJJs; (5) their distri: 
bution is, as maintained by Mennell, inconsistent with their formation as crush- 
1 See Mellard Reade, Lvolution of Earth-Structure. 
