8 HISTORY OF GEOLOGY AND PALEONTOLOGY. 



also gave expression to various hypotheses regarding the 

 relationship of mountain-chains, the action of water, and the 

 presence of the ocean above the continent, as indicated 

 by the occurrence of oysters and other marine organisms 

 in the Libyan deserts on the way to the oasis of Ammon. 

 Eratosthenes taught that the changes of form accomplished 

 by means of water, by volcanoes and earthquakes, and by 

 fluctuations of the sea, are insignificant in proportion to the 

 size of the whole earth. *4 



Thus it will be seen that the majority of the older Hellenic 

 philosophers gave their attention to speculative considerations 

 on the origin of the universe and the earth ; but under 

 the manifold activities of the Roman empire, a new and 

 more realistic spirit became infused into the investigations 

 of the great thinkers. Amongst these the first place must 

 be given to the historian and traveller Strabo (born circa 

 63 B.C.), whose geography, comprising seventeen volumes, 

 was written about the beginning of the reign of Tiberius. 

 Strabo had a thorough mastery of the Greek literature, and in 

 reference to the occurrence of the above-mentioned fossils in 

 the Libyan desert, he agreed with the Greek philosophers that 

 the sea had once covered certain portions of the land, but he 

 also pointed out that the same district may sometimes rise, some- 

 times sink, and fluctuations of the sea-level are associated with 

 such movements of land-surfaces. He further taught that eleva- 

 tions and subsidences of the land are not confined to indi- 

 vidual rocks or islands, but may affect whole continents ; that 

 Sicily, Procida, Capri, Leucosia, the Sirenian and (Enotrian 

 islands had been separated from Italy by earthquakes, and 

 that probably all islands off the shores of continents had origin- 

 ally formed part of the mainland. The oceanic islands far from 

 any mainland have, according to Strabo, been thrown up by 

 subterranean fires. In support of this view Strabo cited the 

 case of a volcanic eruption in the year 196 B.C. between 

 Thera and Therasia. For four days flames rose from the ocean, 

 and as these died down it was observed that a new island 

 had been formed, measuring twelve stadia in circumference. 

 Again, near Methone in the Hermionian Sea, a mountain, 

 seven stadia high, had been thrown up during outbursts of 

 sulphurous vapours and fire; and the town of Spina, near 

 Ravenna, formerly a seaport, was now ninety stadia inland. 

 Strabo is therefore rightly regarded as the father of modern 



