oil the Surface of' the Morca. 3 



Continent, and wholly composed of tertiary deposits, were as 

 yet only shallows. The massive trachytes of Egina, Mithana, 

 Milo, and Santorin were above the water, though not so elevat- 

 ed as they are at present. Each of these islands remained a 

 centre of volcanic operations, which afterwards elevated and dis- 

 ordered the newer tertiary deposits, and which have continued 

 to manifest themselves more or less intensely to the present time. 



On the other hand, a part of the present basin of the Medi- 

 terranean had become terrestrial or lacustrine ; tertiary deposits 

 and " atterrissemens" had united islands, inclosed gulfs, and 

 produced lacustrine and fluviatile deposits, the debris of which 

 we find on the summits of some islands, (as the Archipelago of 

 Iliodroma, Rhodes, &c.) 



In general, however, the narrow zone, having an almost con- 

 stant level, which the tertiary sub-appenine deposit forms round 

 the islands and continents, announces that even at that epoch all 

 the great features of the surface of Greece had been delineated ; 

 and that a general rise, instead of dislocations, would suffice to 

 give it the configuration which it has retained for upwards of 

 four thousand years, without perceptible alteration. 



In consequence of what we have said of the priority of de- 

 pressions of basins closed or open in the interior of the Morea 

 at the time of the deposition of the sub-appeniiie formation, it 

 is evident that they may include the products of the same period, 

 lacustrine, detritic, and alluvial, again covered by a succession 

 of deposits of the same nature, formed during the whole period, 

 even till the present time ; but it would have been impossible for 

 us to recognise and study the succession, if recent fractures of the 

 soil had not formed openings, external or subterranean, for the 

 watersof the closed basins, and had not in consequence caused their 

 denudation. These different effects, the formation and destruc- 

 tion of terrestrial deposits, require, for that reason, a knowledge 

 of the singular hydrogeic system of the Morea, or of the man- 

 ner in which atmospheric water is collected on its surface, and 

 reaches the sea by subterraneous passages. 



This preliminary study will at the same time afford us a more 

 general and natural explanation of the phenomena of continental 

 caverns, and their deposits of osseous breccia ; an explanation 

 which does not require, like that of literal grottoes (see Memoir 

 on the Action of the Sea, &c. Journal dc Geologic, No. 10), 



A 2 



