ANNIVERSARY ADDRESS OF THE PRESIDENT. XCl 



of the whole, Mr. Forbes thinks that certain dotted undulating lines 

 which he has drawn through the vertical fohations will represent 

 the old lines of stratification, and present only a series of undu- 

 latory beds due to upheaval or subsidence, and that he will thus be 

 able to analyse large tracts of gneissic formation hitherto considered 

 irresolvable. 



When we consider the numerous cases where this vertical, or almost 

 vertical, foliation occurs in crystalline and metamorphic rocks, the 

 explanation here given becomes of great importance. At the same 

 time it should be observed, that unless some indication of the ancient 

 stratification is still visible, either in lines of colour or in some change 

 of mineral appearance, it does appear to be rather a bold assumption 

 to imagine a series of lines of stratification of which no evidence 

 exists, merely on the authority of a somewhat parallel system in the 

 Silurian deposits, which at one extremity of the section overlie these 

 metamorphic beds. 



M. Theodor Kjerulf, to whose labours in the field of the palae- 

 ozoic geology of Christiania I alluded last year, has lately com- 

 municated to Sir R. Murchison some additional information on the 

 subject, obtained during the past summer. M. Kjerulf separates 

 the beds of the Silurian basin of Christiania into three divisions or 

 groups, of which the lowest two are decidedly Lower Silurian, and 

 the greater part of the upper group decidedly Upper Silurian. The 

 Hmit between these two groups consists of bands of hmestone and 

 marl, containing Pentamerus in great abundance, and this bed forms 

 a perfect geological horizon throughout the whole district. He has 

 called these groups, in ascending order, Oslo Group, Oscarskal Group, 

 and Malmo Group. The total thickness of these formations is said 

 to be 1930 Norwegian feet (1980 EngUsh), of which 400 belong to 

 the Oslo, 700 to the Oscarskal, and 830 to the Malmo group. He 

 mentions the different localities where these groups are chiefly de- 

 veloped, and describes the contortion of the Oslo group as a great 

 system of waves spread over the original bottom rock of the Chris- 

 tiania basin or valley. This bottom rock is gneiss, mica-schist, &c. 

 The Malmo group is principally developed in the island of that name ; 

 and as the nomenclature of the groups adopted by the author is in a 

 great measure geographical, the true boundary between Upper and 

 Lower Silurian is placed in that group, and near the-hottom. It is 

 difiicult to understand the reasons which have induced the author to 

 adopt this somewhat arbitrary system of subdivision, which, to say 

 the least, introduces some confusion into his classification. It 

 would seem more natural to have retained the lowest bed of this 

 group (9 & 9 5 of the Author's Section) in the underlying group of 

 Oscarskal. 



The connexion between the Malmo beds and the Lower Silurian 

 formations was for a long time obscure ; but the thick beds of cal- 

 careous sandstone (No. 8), with Tentaculites annulatusy Chcetetes 

 {jpetropolitanus ?), and an Orthis cleared up the difficulty, and enabled 

 the author to fix the thickness of the whole formation more accurately 

 than had hitherto been done. The Lower Silurian beds are some- 



