388 H. E. Strickland, Esq., on the Geology 



for these Silurian fossils, and perhaps he rewarded by the discovery of many 

 Trilobites and other organic remains, which I did not meet with. 



The compact limestone of this formation is quarried in several places near 

 the Bosphorus, especially at Baltalimani, where it dips to the westward. In 

 the lower part the strata are thick, but they become thinner upwards, and, 

 after assuming- a concretionary structure, pass into argillaceous schist. The 

 limestone exhibits some very obscure traces of organic remains. 



The sandstones archest exhibited in the cliff between Scutari and Monda- 

 bornou. They are brown, commonly compact, sometimes schistose, and the 

 stratification is distinct, being much broken and distorted. 



The evidence of the organic remains justifies me in referring the forma- 

 tion to the Silurian system of Britain. The occurrence in this remote locality 

 of rocks, which approach so closely to the type of north-western Europe, is 

 somewhat remarkable ; and the more so, as nothing of the kind occurs, as far 

 as I know, in the more southern parts of Asia Minor, or in any portion of the 

 Mediterranean basin. Many geologists are of opinion, that the transition and 

 secondary rocks of northern Europe belong to a different type from those 

 of the Mediterranean basin; and that the characters, both mineral and zoo- 

 logical, of these two parallel series present scarcely any common points of 

 comparison. A line, nearly coinciding with the Pyrenees and Alps, appears 

 to divide these two great basins, if we may so term them. Further investiga- 

 tions may perhaps show, that this line admits of being continued from the Alps 

 through European Turkey to the range of the Mysian and Bithynian Olym- 

 pus ; and this may explain the ap|)earance at Constantinople of rocks be- 

 longing to the type of northern Europe, which are wanting further south in 

 Asia Minor. 



The transition formations, which we have been considering, unite on the 

 north to a mass of igneous rocks, and on the south-west to tertiary deposits. 

 At present, 1 have no clue to the relative age of the two latter, but as the ig- 

 neous rocks are in more immediate relation with the Silurian group, I will 

 notice them next. 



2. Igneous Rocks. 



The igneous rocks of the Bosphorus may be described, in the aggregate, 

 as consisting of trachyte and trachytic conglomerate. On the Asiatic side 

 they commence, en masse, at Kavak under the old Genoese castle, and 

 extend thence lo Yoom-bornou on the Black Sea, or perhaps further. They 

 consist chiefly of angular trachytic fragments, imbedded in a tufaceous paste. 

 The conglomerates, viewed on the large scale, are distinctly stratified ; and 



