304 
Local and detailed lists are added, and detailed sections are given, 
connecting the whole series both with the upper and lower forma- 
tions, especially one from the Possidonia schists and black limestones, 
near Schelke, through the Devonian limestone, and to the lower 
formations exposed on the banks of the Lenne, towards Altena. In 
this section there is no ambiguity, and the defective evidence in the 
sections of Devonshire, when we endeavour to connect the culm- 
measures with the South Devon limestone, is here amply supplied. 
The authors then describe in detail the sections at Paffrath, near 
Bensberg, on the right bank of the Rhine, near Cologne, where the 
same Devonian limestone occurs, with a magnificent series of fossils ; 
its position is, however, reversed, as it seems to dip under the lime- 
stone near Bensberg, which is referred to the upper part of the Si- 
lurian system. 
To the same geological epoch the authors also refer the compli-. 
cated metalliferous deposit of Dillenburgh, and the limestones of the 
Lahn in the country of Nassau. At the former place the great con- 
tortions and the extraordinary intrusions of trappean rocks make the 
relations difficult; but, considered on a great scale, the vast fossil- 
iferous and calcareous group reposes on rocks considered of the Si- 
lurian age: it contains a true Devonian group of fossils, and its 
upper portion at Herbon is surmounted by a Possidonia schist, per-. 
fectly identical with that of Westphalia. The limestones of the 
Lahn at Dietz, Weolburg, Wetzlar, &c., are still more unequivocally 
Devonian ; and though the alternating masses of limestone and schist 
are of enormous thickness (rivalling in that respect the whole series 
of limestones and slates in South Devon), and the sections often 
obscure, yet in descending the Lahn from Dietz to Nassau and Bad 
Ems, they had a proof that the calcareous system is underlaid by 
Silurian rocks. The appearance of these Devonian deposits near 
the eastern limit of the old rocks, on the right bank of the Rhine, is 
accounted for by enormous undulations, which have repeated over 
again, in three or four great parallel troughs, the formations which 
appear in their true place in Westphalia, on the northern limit of the 
same ancient formations. 
§ 4. Silurian System.—The authors next describe the great se- 
ries of rocks which rise from beneath the lower Westphalia lime- 
stone, and state that in the long range from Elberfeldt to Iserlohn 
the descending order is unequivocal. The passage downwards is 
sometimes effected by flagstones, with bands of shale, containing 
thin calcareous courses. In other places, the shales are more abun- 
dant, occasionally becoming much indurated ; and in the range to- 
wards the north-east (for example, near Meschede) this group be- 
comes greatly expanded, and contains many quarries of roofing-slate, 
with a true oblique cleavage. This part of the series is compared. 
with the shales under the Eifel limestone, and with the Wissenbach 
slates, which underlie the Devonian limestone series of Dillenburg. 
The great difference in the development of this group produces a 
great difference in the fossils, but on the whole, they are regarded 
as forming a passage between the Devonian and Silurian types. A 
