AT DIFFERENT GEOLOGICAL EPOCHS. 277 



Elie de Beaumont, we give the names of Jurassic or oolitic 

 sea, and of cretaceous sea, to the waters from which the 

 oolite and the chalk were respectively deposited in soft beds, 

 the outlines of those formations will indicate, for the two 

 corresponding geological epochs, the boundary between the 

 dry land, and the ocean in which these rocks were then 

 forming. Maps have been drawn representing the state of 

 the globe in respect to the distribution of land and water at 

 these periods. They rest on a more sure basis than the 

 maps of the wanderings of lo, or even than those of Ulysses, 

 which at best but represent legendary tales, whilst the geo- 

 logical maps are the graphical representations of positive 

 facts. 



The following are the results of the investigations which 

 have had for their object the determination of the extent of 

 the dry land at different epochs. In the most ancient times, 

 during the silurian, devonian, and carboniferous epochs, 

 and even as recently as the triassic period, the portion 

 of the surface supporting land vegetation was exclusively 

 insular. At a subsequent epoch these islands became con- 

 nected with each other, forming numerous lakes and deeply 

 indented bays. Finally, when the mountain chains of the 

 Pyrenees, the Apennines, and the Carpathians, were ele- 

 vated, about the epoch, therefore, of the older tertiary 

 formations, the great continents possessed nearly their 

 present form and extent. During the silurian epoch, when 

 the cycadese were in the greatest abundance, and the gigan- 

 tic saurians were living, the whole surface of dry land from 

 pole to pole must have been less than it now is in the 

 Pacific and Indian oceans. We shall see presently how this 

 great preponderance of oceanic surface must have contri- 



