TTTE BAllAKAIfS. 
17G 
their matrix these concretions cither atand up as numerous spheres on 
the weathered surfaces, or, if weathorinf;; has l)roken throuf^h the 
outer crust, es|)e(!ially of the lar<fer concn^tions, tliey ffive rise to 
small circular hollows, whence the unaltered core has been removed, 
surrounded l)y a ferru<finous rim. In addition to these concretions, 
infiltration of iron oxides may give rise to the formation of irre- 
gular hard veinlets, horizontal seams, and coatings along joints, of 
iron-oxide-cemented sandstone. Further, in some places, whole beds 
of sandstones are ferruginous, apparently due to tlie deposition of 
secondary ochres and limonite. 
There are fre(}uent variations in the texture of the sandstones, 
which are sometimes coarse grits full of roundi'd, sub-angular, or 
angular fragments of quartz, with fewer fragments of felspar. 
Thin beds are also found composed largely of large fragments of 
white decomposed felspar | to l inch in diameter. Pebble beds 
also occur here and there, and, although they are not of any 
thickness, they make their presence evident by disintegrating into 
large numbers of small rounded pebbles, usually | to 1 inch across, 
scattered over the surface. 
As on the banks, so in the rivers and stream-beds the sand- 
stones usually exhibit a rough, grey surface, with the false-bedding, 
and ferruginous concretions and plates weathering out ; but in 
addition the running water has frequently carved out an extra- 
ordinary number of pot-holes from a few inches up to several 
yards across (Plate 25, fig. 2). 
At irregular intervals in the vertical succession these coarse-grained 
Sandstones under- sandstones contain intercalated beds of coal, 
lying and overlying the shale, and finer-grained sandstones in great 
coal series. variety. Each of these associations may be 
termed a coal series or coal horizon. The sandstones immediately 
underlying each coal series are more argillaceous and finer-grained 
than the generality of Barakar sandstones, being also less massive, 
and indeed often flaggy and well bedded, occasionally showing ripple 
marks. They also frequently possess a greenish or yellowish tint 
due to ferruginous or argillaceous matter. Their deposition seems 
to indicate a slight deepening of the water preparatory to the lay- 
ing down of the coal series itself. 
The sandstones immediately oierlyinr/ each coal series are often 
typical coarse varieties, indicating a rapid shallowing of the water 
after the deposition of the coal. They sometimes contain detrital 
