402 SILUKIA. [Chap. XVI. 
Prussian geologists, which occasionally expands into a deposit of considerable 
dimensions. The limestone which reposes on these schists and sandstones is 
again surmounted by a copious succession of sandstone, mineralogically not 
very unlike many of the lower divisions of the so-called ' Grauwacke,' and 
formerly known under the name of 1 Flotz-leerer Sandstein.' Professor Sedg- 
wick and myself showed that, while the Posidonomya-beds represented the 
1 Culm ' or true Carboniferous Limestone, this ' Flbtz-leerer Sandstein ' or 
1 Jungste Grauwacke ' was simply the equivalent of our British Millstone-grit, 
and that, as in England, it lay immediately beneath the most productive Coal- 
measures. 
This identification was, in truth, one of the most satisfactory assurances 
that a knowledge of organic remains, combined with a clear view of the 
order of superposition, had led us to a correct inference in placing as a 
member of the Carboniferous deposits strata which had previously been 
connected with much more ancient rocks. 
Having thus briefly indicated the character of the rocks which form the 
immediate support of the Upper or productive Carboniferous strata of West- 
phalia and Belgium, it is not my object to attempt any detailed descrip- 
tion of the Coal-measures properly so called. In Westphalia these Coal- 
beds plunge under the Cretaceous rocks upon the east ; and in Belgium 
(as, for example, at Liege) they are at once surmounted by Tertiary de- 
posits. (See Dumont's Maps.) 
Whilst the Devonian rocks of the Bhine, unlike those of Saalfeld (p. 386), 
have afforded few traces of Land Plants, it is important to observe that it 
is specially in this Lower Carboniferous group that nearly all the so-called 
1 transition ' and ' grauwacke ' phytolites described by various German au- 
thors have been collected. Seeing that this series, in the Bhenish Provinces, 
is so very analogous to that of Britain, geologists will indeed be interested 
in comparing the Plants described by Gbppert, Unger, and others with the 
rich flora of the same age found in Northumberland *, Scotland, and parts 
of Ireland. 
Although not adopted by the Prussian geologists in the great map of the 
Bhine Provinces, it is right to mention the opinion of M. B. Ludwig fj 
that the quartzites above Nauheim, which seem to be an eastern prolonga- 
tion of the Taunus Mountains, and repose unconformably upon certain 
Devonian rocks, are (judging from their mode of bedding and mineral cha- 
racter, and, above all, from the large Land Plants they contain) equivalents 
of one of the oldest members of the Carboniferous series. On this point I 
cannot pretend to express a decided opinion without a more elaborate ex- 
amination than I have yet given to the tract. M. von Dechen does not 
adopt this view. 
Inversions. — Inadequate as the preceding brief sketch may be in con- 
* See remarks, by Mr.Q-.Tate, on the Fossil Flora t See 'Eheinische Schiefer-Gebirge,' with a 
of the Coal-formation, in the ' Natural History of map : Jahrbuch der Vereins fur Naturkunde in 
the Eastern Borders,' by Dr. Johnston : 1853. Herzogthum Nassau, (Wiesbaden) 1853. 
