1857-] MURCHISON SILURIAN ROCKS OF RUSSIA. 43 



rian, followed by 8 & 9, or the equivalents of the Llandovery rocks, 

 which connect the inferior and superior divisions. These masses 

 are overlaid conformably by, and pass up into the Upper Silurian 

 series, 10 to 14 inclusive, the whole of which are chiefly charac- 

 terized by fossils of Wenlock and Ludlow species. 



These detailed sections of the strata in the environs of Christiania 

 are most valuable : first, in demonstrating, by comparison, that the 

 Silurian rocks of Norway are, from their base upwards, the true 

 equivalents of those of Britain ; secondly, in pointing out in the very 

 lowest fossiliferous zone the presence of those zoophytes (Grap- 

 tolites) which prevail throughout the series. In the same beds 

 occurs a Lingula, associated with Orthis callactis and other forms 

 which, in Britain, have as yet been found only in the lower part of 

 the Llandeilo formation ; and with these is found the Graptopora 

 flabelliformis, a fossil of the Lingula-schists of Wales : thus showing 

 that, like them, the alum-schists form the natural-history base of the 

 Silurian System. The sections also demonstrate that from this base 

 to the uppermost beds, these zones (in all occupying less than 2000 

 feet in vertical dimensions) represent the whole of the vastly ex- 

 panded British series, and constitute one conformable and natural 

 system, whether viewed physically or zoologically*. 



In addition to the clear order of superposition of the various Silu- 

 rian rocks and their identification by fossils, M. Kjerulf has further 

 shown, how different members of the series have been here and there 

 metamorphosed into crystalline gneiss. The numerous points at 

 which the sedimentary formations have been pierced by eruptive 

 rocks long ago offered to Professor Forchhammer and myself suf- 

 ficient explanation of such conversions f. 



This subject has, indeed, been since worked out in some detail by 

 Mr. David Forbes, whose residence at Christiania has enabled him 

 to contribute satisfactory information, which clearly demonstrates 

 the conversion of sedimentary Silurian strata into crystalline rocks 

 replete with simple minerals %. 



Results of an examination of the Silurian Rocks of Esthonia, 

 Northern Livonia, and the Isle of Oesel, made in the years 

 1853 to 1856. By Professor Fried. Schmidt, of Dorpat. 



The Silurian rocks of Esthonia, Northern Livonia, and the Isle of 

 Oesel, represented in a map which was transmitted to the Society, 

 consist essentially of a series of strata which follow each other in 

 ascending order at slight angles of inclination, and constitute zones 

 trending generally from east to west. These strata have the follow- 

 ing descending order : — 



* Judging from a collection recently transmitted by M. Kjerulf, and which has 

 been examined by Mr. Salter, the specific identification with the British forms 

 may be for the most part depended upon. 



t Quart. Journ. Geol. Soc. vol. i. p. 470, &c, and Kussia in Europe, vol. i. p. 14, 

 note. 



% Quart. Journ. Geol. Soc. vol. xii. p. 166, &c. 



