72 Transactions of the South African Philosophical Soctety. 
the black shales are invariably overlaid by lighter coloured softer 
shales, a thin cherty band occurs some distance from where the black 
shale is met with at Grootfontein, and this is again met with at the 
junction of the Orange and Vaal Rivers. These facts indicate that 
over an immense area and under exactly similar conditions these 
beds were deposited, possibly in a very extensive shallow lake. 
In my 1886 edition of the Geological Map I included within the 
Stormberg coal measures all the coal outcrops then known, but 
recent facts necessitate an alteration of the boundary, and it will 
be interesting to make out the proper extension northward of the 
Stormberg coal measures. 
THE CoaL SEAM. 
At Vereeniging the coal seam is as follows: At the base is the 
Dwyka conglomerate known locally as ‘fireclay ”’ ; it is about 50 feet 
thick and rests upon Lydenburg Beds. This conglomerate is thickly 
studded with boulders, pebbles, &c., that are striated and glaciated. 
The upper portion shades gradually into a carbonaceous sandy shale 
in some places, and is thickly penetrated with root-marks runnin 
vertically into it, the general surface being fairly horizontal. This isa 
true ‘‘underclay’”’ or ‘“‘ seatstone,’ and it is locally termed ‘‘ fire- 
clay ’’ because the upper portion when separated from the stones is 
made into firebrick, &c. This conglomerate is rudely bedded. 
Above the conglomerate in places there is a bed of black shale 
with plant remains. The top of the shale is uneven, and then comes 
the coal seam, which ranges from 6 feet to 15 feet thick and 
averages 9 feet. The coal is much laminated and hard; thin bands 
of iron pyrites occur near the top of the seam. A thin parting of 
sandstone 1 inch thick occurs about 3 feet below the roof. (A 
similar parting is found in Mr. Sawyer’s 54 feet coal seam). 
Pebbles and boulders are found embedded in the coal at al 
horizons; these are in some cases clearly glaciated. 
Above the coal is a band of conglomerate from 1 inch to 18 inches 
thick, with small pebbles principally, but at frequent intervals pebbles 
of large size and some boulders occur, some of them partly embedded 
in the coal and partly in the conglomerate forming the roof of this 
coal seam. Many of the pebbles are striated and glaciated. 
Just above the conglomerate are black micaceous shales thickly 
studded with the interlaced stems of calamites, the former plant 
now represented by a flattened thin seam of coal. There must have 
been a dense forest of these plants to supply the prodigious number 
of prostrate stems. In width these casts range up to over 12 inches, 
and in length up to 60 feet. The stems are fluted lengthways, and 
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