346 
SILUEIA. 
[Chap. XIV. 
which nothing organic has been discovered, are covered at intervals by true 
representatives of the Silurian rocks. I have little doubt that the oldest of 
these rocks, particularly in the central and northern parts of Norway, tracts 
which I did not visit, will be found to underlie all the formations of Cambrian 
and Silurian age, and therefore pertains to the Laurentian. 
The lowest strata which have as yet afforded fossil animal remains are 
clearly the equivalents of the Lowest Silurian strata of the British Isles, Bo- 
hemia, and other countries. 
In a recent tour in Norway, made to compare the effects of glaciation in that 
country with those known in Scotland *, Mr. Geikie ascertained from the com- 
munication of M. Tellef Dahl, who with M. Kjerulf is carrying out the Geo- 
logical Survey of Norway, that there was also a great similarity in the general 
succession of the rocks of the two regions. Thus the Laurentian gneiss is re- 
presented by the widely spread crystalline rocks of Telemark, covered by red 
sandstone and conglomerates (probably Cambrian), which lie quite unconform- 
ably on the fundamental gneiss. Then follow schists with Dictyonema Norvegica, 
which may stand for the ' Primordial' Silurian zone. The last is surmounted by 
quartzites, and hornblendic and even gneissic schists, resembling the altered 
Lower Silurian of the Highlands of Scotland, and are manifestly of the same age 
as the unaltered Lower Silurian strata near Christiania. Other rocks, representing 
the Lower Old Eed Sandstone of Scotland, surmount all the preceding series. It 
may be added also that, in Kjerulf and Dahl's new Geological Map of South Nor- 
way, a large area of green mica-schist, that was formerly thought to be azoic, is 
really composed of Silurian metamorphic rocks, in which obscure fossils, such 
as an Orthoceras and a Coral, have been detected. Also the extensive tract of 
sandstones, grits, and conglomerates, once regarded as Devonian, in the same 
region, are of Cambrian age, resting on Laurentian gneiss, and are much more 
extensive than the earlier maps depict them. 
The first of the following diagrams represents the succession of Lower Silu- 
rian deposits from a base of crystalline gneiss and associated strata near Kinne- 
kulle in Sweden f. 
Lower Silurian Strata of Sweden reposing on Gneiss. 
(From ' Eussia-in-Europe,' p. 15.) 
d. Black Graptolite- 
schists. c. Orthocera- 
tite-limestone. b. Alum- 
slates, a. Lowest or 
Fucoidal Sandstone. 
gn. Gneiss. 
t. Trap or eruptive greenstone. hi. Erratic blocks. 
In other parts of Sweden, as near the Billingen Hills, the two lower groups 
of strata, a, b, of the above section are seen to rest upon granitic rocks without 
* See Proc. Eoy. Soc. Edin. vol. v. p. 532. 
t A detailed geological map, including all the 
crystalline and metalliferous rocks of Sweden, has 
for some time been in preparation, but is as yet 
only partly published. This task was undertaken 
by MM. Forsells,Erdmann,Franzen, and Troilius, 
but abandoned. M. Erdmann, who has lately vi- 
sited England, has now taken it up by authority, 
and will, I trust, complete this work. 
