392 
SILURIA. 
[Chap. XVI. 
Silurian types, chiefly those of Bohemia. When we add to these data the 
striking fact that a Graptolite has been found by M. Bischof in the slaty schists 
east of Harzgerode, and that M. Ad. Romer has detected Graptolithus priodon, 
Bronn, with other species of that genus in the slaty schists of the Western 
Harz and in other parts * there can no longer be any doubt that, although their 
limits are not yet defined on any map, the Upper Silurian rocks have a real ex- 
istence in this chain. A large portion, therefore, of the tracts laid down as 
'Culm' in Adolf Roiner's Geological Map of the Harz must, as that author 
has candidly stated, be changed to Silurian, whilst other parts of this so-called 
1 Culm ' will pass into the Devonian group. Besides the underlying Upper 
Silurian rocks, the hill of the Rammelsberg near Goslar is known to be of 
the oldest Devonian age (Spiriferen-Sandstein), whilst the limestones and 
iron- ores around Elbingerode, and certain masses in the Lauther-Thal, at Abte- 
nau &c, are proved by their fossils to be of the Middle-Devonian or Eifelian 
age f- These are succeeded, first by Upper Devonian, and next by slaty masses 
formerly included in the 1 Grauwacke ' of the Germans, but which Sedgwick 
and myself first identified with the Lower Carboniferous of Britain, and notably 
with the Culm of Devonshire. Referring to our old memoir J for the estab- 
lishment of that identification, I may say that many years must still elapse 
before the demarcation between these deposits can be even approximately de- 
fined in a region so replete with disturbances, and in which fossils are detected 
at wide intervals only. 
In truth, through the combination of many disturbing causes, the chain of the 
Harz has literally been riven into detached fragments, the relative age of which 
can very rarely be proved by order of superposition, and can be interpreted only 
through a close examination of the organic remains of each broken mass. In 
the Rhenish Provinces, on the contrary, though large portions of their strata are 
infinitely contorted and broken, and sometimes even inverted, the Northern or 
Westphalian frontier exhibits a perfect and complete succession of formations 
in their normal and ascending order. The reader's attention will therefore be 
now directed to that region. 
Palaeozoic Rocks of the Rhenish Provinces of Prussia, and of Belgium. — 
The convoluted and broken rocks presenting such an antique slaty aspect, 
and, crowned with castles, forming the chief features of the gorges of 
the Rhine and the Moselle, exhibit nowhere any fossiliferous band so old 
as the Upper Silurian of the Harz. This remark applies to all the terri- 
tory on the right bank of the Rhine, from the Taunus Mountains on the 
south-east, to the Coal-fields east of Diisseldorf on the north-west, and 
also to a large portion of Belgium. This vast tract of formerly undi- 
vided * Grauwacke,' including the Duchy of Nassau, and having its northern 
frontier in Westphalia, is bounded on the east by the Secondary rocks of 
Hessia, which range southwards by Marburg and Giessen to Frankfort. 
On the left bank of the Rhine, the same upward succession occurs between 
the Lower Devonian rocks of the Hundsriick on the south-east, and the 
Coal tracts of Aix-la-Chapelle and Belgium on the north-west. It is only 
by deflecting westward into the mountainous tract of the Ardennes, that 
* ' G-raptolithen am Harze, von Prof. Fr. Ad. t See Quart. Journ. Geol. Soe. Lond.vol.xi. p.439. 
R<5mer,' Leonhard und Bronn's Neues Jahrbuch, J See Sedgwick and Murchison, Trans. Geol. 
1855, p. 540, plate vii. Soc. Lond. ser. 2. vol. vi. pp. 235 &c. 1839. 
