742 RAS. PENROSE sie 
few feet of intervening strata; in fact the two sometimes seem to come 
together. It varies from a few inches to several feet in thickness, 
but is usually thin, though often rich in gold. Sometimes, especially 
on the eastern part of the Witwatersrand district, a very persistent 
slaty parting occurs between the Main Reef and the Main Reef Leader, 
and is locally known as ‘‘the interbedded dike.” Another small 
conglomerate, the South Reef Leader, lies immediately under the 
South Reef, and is also often rich in gold. The Middle Reef is a 
very low-grade body of conglomerate ore lying between the Main and 
South Reefs; and the North Reef is also a low-grade bed lying below 
the Main Reef. 
Sometimes still other conglomerate beds than those mentioned 
occur, while at other times some of the beds mentioned are wanting. 
In fact the conglomerates are more or less lenticular strata, widening 
and thinning at intervals, and sometimes disappearing altogether. 
In some places two or more beds may blend into one, or any one bed 
may be split up into two or more beds separated by quartzite; so that 
in different localities, a different number of conglomerates may be 
found, and those that have been described above are simply those 
that are usually the most continuously represented. Sometimes what 
seem to be the same conglomerates change their positions slightly 
in the associated strata and are a little higher or a little lower in one 
place than in another, while sometimes the formation is very much 
faulted, so that it is often difficult to correlate certain beds in different 
places. On the whole, however, the conglomerates, as comparéd with 
conglomerates elsewhere, may be said to be remarkably continuous 
over long distances, and this feature of the ore bodies has been one 
of the chief factors in the wonderful development of the mining opera- 
tions of the region. 
- Though the conglomerates mentioned all carry gold, yet the 
quantity varies considerably in the different beds and even in dif- 
ferent places in the same bed. The main Reef, though large, is 
generally of rather low grade, but it is worked in many places at a 
good profit. The South Reef and the Leaders are usually of higher 
t Some of the reefs mentioned here are sometimes known by different names in 
different parts of the district, but the names given above are those most commonly 
used. 
