Observations on the Occurrence of Anthracite. — Gresley. 15 
mountainous rim, of which the outcrop of the thick and mas- 
sive conglomerates forms the core, the Choctaw basins are 
enclosed by a ridge, sharp and bold in places, but rarely 
mountainous, formed by the outcrop of the basal sandstone. 
Whether this rock is the equivalent of the Conglomerate or 
not is yet wholly conjectural." In this coal field analyses 
show the coal to be least anthracitic in the west and most so 
towards the Kavanaugh mountains on the east, in which di- 
rection also the greatest pile of Coal Measures occurs. 
XI. European Anthracite Regions. 
The Irish- South- Welsh coal field. That we have good 
grounds for supposing the southern Irish anthracitic basins 
were originally part of the South Wales coal field few if any 
will deny. Now, as is well-knowm, the anthracitic portions of 
the latter region and all the Irish anthracite is topographically 
and stratigrapically very similar, that is to say both are adja- 
cent to or flank regions composed of pre-Carboniferous rocks 
of great vertical thickness, though now much folded and enor- 
mously planed down by denudation. The South Wales Coal 
Measures, and perhaps the Irish too, are characterized by 
thick and very numerous strata of sandstone and of grit.* 
Some 12,000 feet is the reported thickness of the Coal Measures 
in Glamorganshire. Is there any reason to suppose that this 
thickness was less where Pembrokeshire, Carniganshire, or 
the St. Georges channel now are? It is true the Devonian 
series thins out in a westerly direction below the South Wales 
coal field. Furthermore the Silurian, Cambrian and older 
rocks of this region of Great Britain are, in a sense, metamor- 
phosed, and local streaks of anthracite are known to occur in 
the Silurian. A reference to the generalized sections herewith 
shows the author's idea as to where the greatest original 
thickness of Carboniferous rocks perhaps was, namely, — 
where the channel is now (see section No. 1). No. 3 shows 
Ireland and South Wales above sea level with the anthracitic 
regions as now remaining after the general upheaval and con- 
sequent crumpling and faulting (seen in section No. 2) and so 
largely removed where the curved dotted lines are in section 
3. If my views in regard to these formations and changes 
be something like correct then the inference is the thickest 
*See Mem. Geol. Surv. of G. B., vol i, paper by De la Bdche. 
