162 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Jan. 31, 



These views developed the existence of a vast trough or elongated 

 basin of Silurian strata, the direction of which lengthwise is from 

 S. and by W. to N. and by E., and which in the parallel of Christiania 

 has a width of about thirty English miles. This trough was shown 

 to consist of two low tracts, on either side of a high intervening 

 plateau ; each lower lateral tract being composed of a full series of 

 all the Silurian strata (Lower and Upper) ; and the central higher 

 ground, of Old Red Sandstone or Devonian strata. 



This exposition of a symmetrical order, from the base of the 

 stratum containing the oldest known remains through Lower and 

 Upper Silurian rocks, and thence through about a thousand feet of 

 overlying red sandstone, was naturally dwelt upon by me with great 

 satisfaction : for, in exploring the remaining parts of Scandinavia 

 where such palaeozoic formations were present, no other district could 

 be discovered in which so complete and continuous a succession was 

 to be seen. The great Russian Empire exhibits no such clear 

 Silurian base as this Norwegian trough presents ; whilst even the 

 symmetrical Silurian basin of Bohemia, so justly celebrated through 

 the labours of M. Barrande, is inferior in one respect, — viz. in not 

 exposing, like the Norwegian example, a great overlying mass un- 

 equivocally of Devonian age. 



Although my explanation of this order, as first given at the 

 Meeting of the Scandinavian Men of Science in June 1844, was 

 warmly approved by my associates who were present (including 

 Leopold von Buch, Berzelius, and Forchhammer), it met with an 

 opponent in M. Keilhau, who, though he had published his * Geea 

 Norvegica ' and a map of Norway which is very praiseworthy for 

 its mineral features, maintained ideas essentially distinct from my own 

 respecting the consecutive order ; and who still, as I understand, 

 does not admit the metamorphism of some of the Silurian strata into 

 crystalline slate (harte-schiefer) — a point I endeavoured to explain 

 satisfactorily to this Society many years ago. 



Under these circumstances, I have long wished to see some 

 free Norwegian arise, who, looking fairly at nature, would say 

 whether the order I had indicated was exact, or if not, who would 

 correct it ; and who would further test it by a close examination of 

 the strata, and by laying down their outlines on a map. 



Fortunately, I met with Mr. David Forbes, the brother of our 

 universally beloved and respected former President, and, finding that 

 he was frequently at Christiania, I urged him to produce before the 

 Geological Society some fruits of his own observations on the rocks 

 of Norway. 



I also particularly requested him to obtain some data of detail 



the first explanation of the true order of the region. In fact, whilst the memoir 

 of M. Kjerulf contains much valuable new matter, particularly his descriptions and 

 analyses of the igneous and metamorphic rocks, and also lucid diagrams explana- 

 tory of the physical relations of the strata, his chief sections {ea;. gr. those of 

 p. 51) are, as he himself states, analogous to that general transverse section which 

 I offered to the Christiania Meeting of 1844, and which was repeated in the 

 above-mentioned works, and lastly in mv ' Siluria ' of 1854, pp. 319, 320. — 

 [R. I. M. May 23, 1855.] 



