ANNIVERSARY ADDRESS OF THE PRESIDENT. 189 



and of Mr. Lyell on America, and in a very valuable memoir by 

 M. Virlet. As far as my limits will allow, I will bring forward some 

 of that evidence. 



With limited exceptions, true granites are rarely found in the 

 higher portions of the Urals, but they are of frequent occurrence 

 in the lower regions, particularly on the Siberian side. The igne- 

 ous rocks that enter into their composition are different forms of 

 syenite, porphyry, greenstone, and felspar rocks, often graduating 

 into each other, and associated with serpentine. These have evi- 

 dently been erupted at different periods ; and there are wide tracts 

 occupied by granitoid rocks, which appear to have been erupted 

 after the age of the carboniferous series, and posterior to the greater 

 proportion of the greenstones and other eruptive rocks of the Urals. 



It was only after Sir R. Murchison and his companions had be- 

 come thoroughly acquainted with the slightly consolidated and un- 

 broken sedimentary deposits in European Russia, that they were 

 able to decipher the intricate characters of the indurated and cry- 

 stalline strata which constitute the flanks, enter into the very body, 

 and form lofty serrated ridges of the Ural chain ; broken up and 

 cast about in much apparent confusion. But from the presence of 

 organic remains, traceable at intervals along both flanks, and even 

 close to the axis of the chain, they were satisfied that some of the 

 central ridges, although composed of chloritic, talcose, micaceous, 

 and quartzose slates, cannot be of higher antiquity than the uncon- 

 solidated Lower Silurian rocks on the shores of the Baltic ; and that 

 others, although in a highly crystalline state, are not older than the 

 Devonian and carboniferous series. The same rocks, when they 

 recede from the great lines of eruption, resume their ordinary sedi- 

 mentary characters. In one place the authors expressly say, that 

 in proportion as they receded from the igneous zone, the sedimentary 

 strata gradually parted with their talcose, chloritic and quartzite 

 characters, and assumed the appearance of ordinary argillaceous 

 schist, with bands of grit and sandstone, all parallel to the crystal- 

 line axis of the chain. In another place they describe certain Upper 

 Silurian beds, consisting of alternations of argillaceous slate and 

 black encrinite limestone, passing into talc-schist, and containing 

 great flakes of mica. Between two great parallel lines of eruption 

 they saw pure white saccharoid limestone containing Encrinites, and 

 associated with other crystalline beds, which they were satisfied 

 were once sandstones formed under the sea in the palaeozoic period. 

 In like manner the sedimentary rocks on the northern frontier of 

 Russia, where they approach the great granitic and trappean region 

 that stretches southward from Russian Lapland, become so changed, 

 that the shales are converted into Lydian stone, the limestones into 

 marbles, and the sandstones into indurated and sometimes granular 

 quartz. These are not partial local effects, but characterize a long 

 line of country in a broad zone. The authors observe, that " the 

 thorough examination of tliis great band of Silurian rocks, more or 

 less metamorphic, which lies between the purely crystalline or azoic 

 rocks of the north and the wholly unaltered Devonian and carbo- 



