GEOLOGY (OF THE SOGUTH ARRICAN REPUBLIC 13 
series of sandstones and conglomerates, neglecting possible 
reduplication by faulting, is given as 17,000 to 18,000 feet. 
Schmeisser enumerates in this series some seventy beds of 
conglomerates, of which by no means all contain gold, and of 
those that do, comparatively few have enough to pay for work- 
ing, or are payable, as the South African phrase is. They are 
generally divided into groups or series of reefs, of which Hatch 
gives four in descending order beneath the Black reef series, 
viz., the Elsburg series: the Kimberley series: the Livingstone 
and Bird series: the Main reef series. The latter is that upon 
which the principal mines are working today. Beneath the 
Main reef series is the Dupreez or Rietfontein series, two and 
one-half miles north of Johannesburg, which has only been 
traced 10,000 feet along its strike, whereas the Main reef series 
has been traced more or less continuously for forty-five miles on 
the strike. Across the strike from the Dupreez outcrops to those 
of the Black reef series, is eight to ten miles. 
As shown by the underground workings these gold-bearing 
beds are traversed by dikes and sheets of greenstone and con- 
siderably faulted. 
Twenty-five miles south of Johannesburg, in the Heidelberg 
region, they are working on a series of a similar conglomerates, 
which dip 30° to the northward, and are assumed to belong to 
the south side of a syncline. It has not been possible, however, 
to correlate the Heidelberg and neighboring Nigel series with 
those outcropping in the Johannesburg region. Going eastward, 
on the strike both these and the southerly dipping beds pass 
within a few miles under the horizontal coal beds of the Karoo 
formation. The Johannesburg series have been proved under 
these beds by borings, and are assumed to curve round to the 
southwestward and find their continuation in the Nigel and 
Heidelberg fields. To the westward again the Johannesburg 
beds, at a distance of fifteen to twenty miles from the city, bend 
to the southwest, toward Potchefstrom and Klerksdorp where 
similar conglomerates outcrop. The outcrops thus form a sort of 
horseshoe curve. It is naturally a matter of great importance 
