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



Section north side of Anadoli-fanar. 



Lighthouse. 



th vulcaniu buwlders. 



On the European side of the Bosphorus, the igneous rocks commence on 

 the north of Buyukdere. Here a species of trachyte of a yellow colour 

 forms some considerable hills. It is much decomposed, and resembles loose 

 sand, when viewed at a distance. Further north is a series of conglomerate 

 beds, similar to those of the Asiatic side, and extending to the Black Sea. 



These are the general features of the mass of igneous rocks, which abuts 

 against the northern flank of the Silurian schists above described. The works 

 of MM. Andreossy and Pontanier contain some information on their mineral 

 contents. 



A variety of trachytic and trap dikes occur in the Silurian schists, and are 

 doubtless connected with the general mass of igneous formations. At Balta- 

 limani and on the hills above Bebek, a ferruginous decomposing trachyte ap- 

 pears in the midst of the schistose rocks. At Kiretch-bornou is a dike of fine- 

 grained greenish trap, about 15 feet in thickness, cutting through strata of 

 calcareous and argillaceous schist. A similar dyke occurs in the limestone 

 quarries at the base of the Giant's Mountain. It is perpendicular, 4 or 3 feet 

 thick, and from the removal of the limestone on each side, it resembles a 

 wall running across the quarry. Some fragments of limestone occur in the 

 midst of the trap, but neither they nor the rock on each side of the dike, show 

 any signs of alteration. 



Lower down in the quarry, near the level of the Bosphorus, are some masses 

 of greenish and white quartz rock, which have more the appearance of an 

 altered sandstone than of an igneous injected rock. 



3. Tertiary Formation. 



This formation commences immediately on the west of Constantinople, 

 and extends along the north coast of the sea of Marmora for many miles, its 

 western limit being at present undetermined. On the west side of Constanti- 

 nople the formation ranges inland for about three miles, till it meets the trans- 

 ition series, but the nature of the junction is not exposed by any section, 

 which I could meet with. 



The beds are best exhibited in the quarries at Baloukli and Makri-keui ; 

 where they consist of soft white shelly limestones and marls, resting on sand 



