58 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



13. Greyish shale or claystone, stratified, for 15 yards, and dipping about 



N. 65° E. 



14. Soft yellowish stone with ironstone for 13 yards, much contorted. This 



stone has no appearance of stratification, and does not apparently belong 

 to the same age of rocks as the adjoining shales. 



15. Trachytic rocks, already mentioned above. 



Having now described the whole of the Primary strata of the 

 island, it will be readily seen that, setting aside the variations and 

 contortions of the beds in the vicinity of the trachytic rocks, a dis- 

 tinct ascending order of Primary strata can be traced from the north- 

 eastern to the south-western jJortion of the island. 



The fossiliferous argillaceous strata of the series form but a thin 

 imperfect band as compared with the great mass of quartz rocks-, 

 of which almost the entire body of the San George Mountain is com- 

 posed; but they are sufficient to fix their age as true Devonian 

 strata. I shall reserve any further remarks as to their exact posi- 

 tion in the Devonian series until the description of the adjoining 

 island of Andirovitho has been given, where much additional evidence 

 has been discovered. 



The question of the origin of the quartzose rocks met with on the 

 Bosphorus and in the adjoining islands is clearly solved on the 

 south-east coast of Prinkipo ; for we find those rocks interstratified 

 there with other beds of a di 5*6 rent character ; whilst on the very 

 top of the San George there is a thick bed of conglomeratic quartz 

 composed of large rounded boulders, which is evidently the remains 

 of an ancient sea-beach. The sandstones of the series have, in fact, 

 been metamorphosed into a solid quartz rock. 



And could not the phenomenon of the ironstone at the junction 

 of these rocks and the trachytes be accounted for also by the total 

 absence of this substance in the quartz, when we kuow that sand- 

 stones generally contain a considerable proportion of iron ? Could 

 it not have been melted out of the adjoining sandstones by intense 

 heat at the time of the eruption of the trachytes, and run off into 

 these rocks ; just as iron is extracted from the ore by smelting in 

 modern times ? 



3. Island of Andirovitho. — This island is situated on the eastern 

 side of Prinkipo, and measures about 1100 yards in length by 600 

 yards in extreme breadth. T\''ith the exception of a small spot of 

 cultivated land at the extreme end, the island is barren and rocky, 

 and its greatest height above the sea-level does not exceed 60 or 

 70 feet. 



The strata are composed entirely of sedimentary rocks, and, from 

 an inspection of their enclosed fossils, are of Devonian age ; and they 

 are exceedingly interesting as exhibiting an entirely new series 

 compared with that of the Bosphorus, the fossils also being found 

 here in a much more perfect state of preservation. Limestone is the 

 prevailing stone of the island ; and some of the beds are of great 

 thickness and purity. Here a profusion of corals is to be seen, 

 and in so much more abundance than anywhere on the Bosphorus 

 or the adjoining mainland, that these strata may mth propriety be 



