\ 
14 Scientific Proceedings, Royal Dublin Society. 
impregnated with iron pyrites, the gold being obtained from 
the cementing matter. The pebbles vary greatly in size, ranging 
from the size of a small marble to that of a turkey’s egg. 
2. Bird-reef series.—These consist of eight beds of conglomerate. 
In some places gold is found in paying quantity, but the series 
“has not yet been fully prospected. 
3. Kimberley series.—These consist of a large van hea of 
conglomerate beds varying in thickness. 
South of Florida, the Kimberley-reef proper is about 100 
feet thick, gold in paying quantities not having hitherto been 
discovered in it. 
4, Elsburg series.—These consist of a large number of beds of 
considerable thickness, and here, too, gold in paying quantities 
has not been met with. 
Each and all of these series are accompanied by their own 
particular characteristic pebbles, by which they are easily recog- 
nized. 
Overlying the Elsburg series, an extensive sheet of amygda- 
loidal diabase is found, forming the Klipriviersburg, the Black 
reef resting on this formation, with the dolomitic limestone 
superimposed. In succession appears the Magaliesburg quartz- 
ite sandstone. North of the Main-reef series, in the vicinity of 
Rietfontein, a thin bed of conglomerate is encountered, called Du 
Preez reef, on which successful work is being carried on. 
The Black reef series.—This consists of quartzites which lie 
unconformably on the Banket series, the angle of dip ranging from 
5° to 15° from the horizon. ‘Faken as a whole, this reef is remark- 
ably “‘ patchy,’ and varies in thickness from that of a single pebble 
to 5 feet. In some places the reef is absent. The pebbles are 
cemented with the sulphides and oxides of iron. 
The Dolomitic Limestone. —This overlies unconformably the Black 
reef. In appearance it is bluish grey, and contains a large percen- 
tage of magnesia. Numerous siliceous beds occur, running through 
it, conformably with the stratification. Quartz veins destitute of 
gold are also found, cutting through the strata. Underground 
cavities also form a characteristic of the group. The thickness of 
this dolomitic limestone may be set down at about 10,000 feet. 
The Magathesburg series.—This consists of quartzites, sandstones, 
and shales, which form the hills known as the Magaliesburg range. 
