SUBTERRANEAN GEOLOGY OF SOUTH EASTERN ENGLAND. 143
and Devonian age, while the rest of Belgium, on the north, mainly
consists of Secondary and Tertiary rocks, though close to the Coal-
measures patches of older rocks may occasionally be seen. The
best series of sections obtainable across the Palaeozoic rocks of
Belgium is that along the course of the river Meuse between Givet
and Namur, though it is better to cross the French frontier and
begin the inspection at Fumay, thence proceeding northward by
Givet and Dinant to Namur.1 At Fumay the rocks are of Cambrian
age, but these are soon succeeded by Devonian and Lower Car-
boniferous beds. Near Dinant there is a synclinal basin con-
taining Coal-measures. Close to Namur a thin band of Silurian
rocks appears, bounded on its northern side by a fault. North
of this fault is a second and much more compressed basin of
Devonian, Lower Carboniferous, and Coal-measure rocks; Silurian
strata appearing on the north as well as the south of this basin. We
have thus, between Fumay and Namur, two synclinal basins, that of
Dinant and that of Namur. The Dinant coal basin is of no econo-
mical importance and does not extend far westward, while the coal
of the basin of Namur is that worked in the Boulonais. A singular
feature of this basin of Namur is the way in which it has been folded
and crumpled up by immense pressure from the south northward;
and along the line of fault which forms its southern limit, and which
"hades" or is inclined towards the south, the Silurian band known
as the Condroz Crest has been thrust upwards, till it overlies the
Devonian and Carboniferous rocks. This fault is known as the Great
Fault, or Eifelian Fault, and bounds this coal-field on the south
from Liege as far as Marquise in the Boulonais,2 and along its line
Coal-measures are met with under Devonian rocks both in Belgium
and in France. Prof. Prestwich ("Quarterly Journal of the Geo-
logical Society," 1878, vol. xxxiv., page 904) gives an account of some
borings made in search of coal at Auchy-au-Bois, near Lillers, in the
Department du Pas-de-Calais. Borings for coal westward of Bethune
had ended either in Carboniferous Limestone or Devonian rocks, to
the discouragement of their directors. Certain geologists, however,
ventured to think that at Auchy-au-Bois there might be found a
reversal of the strata like that at Namur, and that consequently Coal-
1 See "The Geology of Belgium and the French Ardennes." Papers by Prof J. Gosselet,
Prof. T. G. Bonney, A. Rutot. E. Van Den Broeck, and W. Topley. Published by the Geol.
Assoc, 1885. Prof. Gosselet's Paper has been translated by Miss Mary Forster.
2 In Proc. Geol. Assoc, January, 1879 (vol. vi., pp. 1-37), is "A Geological Sketch of the
Boulonais,'' by Dr. Charles Barrois.