218 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [JlUie 17, 



the freshwater series ; but, as the quarries of Makri Keui not far 

 distant are in a white lacustrine limestone, as Mr. Strickland long 

 ago pointed out, I am inclined to consider the Stephano marls as 

 freshwater also, since I have found no evidence of any marine ter- 

 tiary in the shores of the Sea of Marmora. In some specimens which 

 I procured from the quarries of Makri Keui are casts of a Melania, 

 apparently resembling the one I procured from the neighbourhood of 

 Vourla in the Gulf of Smyrna, figured in the ' Geological Journal,' 

 vol. i. p. 163. 



The above evidences of the freshwater origin of the deposits which 

 line the north shore of the Sea of Marmora seem to justify my view 

 of connecting the basin of the Sea of Marmora and the Archipelago, 

 as having been a part of one great lake, which probably covered a 

 great portion of the central part of Asia Minor, as shown by Hamilton 

 and Tchihatcheff, penetrating by the valley of the Hermes and the 

 other valleys separating the older chains and ranges, as Xanthus on 

 the south, the Halys on the north, and the Hermes on the west. 



The lignite-beds, briefly noticed by Mr. Poole*, in the Nikomedian 

 and Brusa valleys, are, I think, a portion of the same lacustrine 

 series, which seems to ^represent a long portion of the middle and later 

 Tertiary periods ; although the relative age is difficult to determine 

 precisely, on account of the great permanency of genera and species 

 of the air-breathing Mollusca peculiar to the freshwater fauna. 



As the two basins of the Archipelago have each their central, but 

 extinct, volcanos, or foci of eruption, in Santorin and Lemnos, so the 

 Sea of Marmora has its focus in Pacha Liman and the Kutali Islands, 

 which both seem to have been volcanos, from being entirely composed 

 of granitic trap, and presenting a crater-like form. It is also an in- 

 teresting fact, that, as there is very deep water in the neighbourhood 

 of these sudden uplifts of igneous rocks, or abrupt uprisings of the 

 bottom (as also occurs near Micero and Methana, two other evident 

 volcanos of no very early date), so there is in the centre of the Sea 

 of Marmora a sudden depth of 300 and 400 fathoms (representing, 

 perhaps, a downcast proportionate to some neighbouring great uplift 

 of the strata) ; and Marmora Island in its south-western half shows 

 a large mass of granitic and porphyritic trap, associated with crystal- 

 line limestones and micaceous shales and schists that resemble rocks 

 of the earliest age. 



The section, fig. 4, p. 213, taken along the coast, and touching at 

 several spots, tends to confirm these views. 



The marble-quarries of Marmora are celebrated ; and I found 

 them as extensive as the Pentelic Quarries of Attica, with the marble, 

 in some parts, quite as white, pure, and crystalline as the Parian, but 

 generally more resembling the cippoiine of Carysto. 



As this condition occurs only when a volcanic dyke of the por- 

 phyritic trap comes in proximity with the limestone, as seen in the 

 section, it seems to show that these rocks owe the oldness of their 

 aspect to their metamorphic condition ; and I am inclined to think 

 that the eruption of igneous matter in contact with them may be of 

 * Quart. Journ. Geol. Soc. vol. xii. p. 1. 



