528 CAUSES PRODUCING BASINS. 
form of Troughs or Basins have resulted from two 
distinct systems of operations, in the economy of 
the terraqueous globe ; the first producing sedi- 
mentary deposits, (derived from the materials of 
older rocks, and from chemical precipitates,) on 
those lower spaces into which the detritus of an- 
cient elevated regions was transported by the 
force of water ; the second raising these strata 
from the sub-aqueous regions in which they were 
deposited, by forces analogous to those whose 
effect we occasionally witness, in the tremendous 
movements of land, that form one of the pheno- 
mena of modern Earthquakes. 
have shewn us the links which connect the Carboniferous system 
with the older Slaty rocks. The large group of deposits to which 
he has given the appropriate name of Silurian system, (as they 
occupy much of the Territory of the ancient Silures,) admits of 
a four-fold division, which is expressed in the section PI. 66. 
Fig. 1. This section represents the exact order of succession of 
these Strata in a district, which must henceforth be classic in the 
Annals of Geology. 
In September, 183.5, I Tound the three uppermost divisions of 
this system, largely developed in the same relative order of suc- 
cession on the south frontier of the Ardennes, between the great 
Coal formation and the Grauwacke. See Proceedings of the 
Meeting of the Geological Society of France at Mezi^res and 
Namur, Sep. 1835, {Bulletin de la Sociiti G'eologique de France, 
T om. VII.) The same subdivisions of the Silurian system, main- 
tain their relative place and importance over, a large extent of 
the mountainous district of the Eifel, between the Ardennes and 
the Valley of the Rhine ; and are continued East of the Rhine 
through great part of the duchy of Nassau. (See Stiffts Gebirgs- 
Karte, von dem Herzothum-Nassau. Wiesbaden, 1831.) 
