28G c )SMos 



Btored to a portion of its contested right and title tD be consid 

 orctl as a primordial rock. 



The recent progress of geognosy, that is to say, the moro 

 extended knowledge of the gcognostic epochs characterized by 

 difference of mineral formations, by the peculiarities and suc- 

 cession of the organisms contained within them, and by the 

 position of the strata, whether uplifted or inclined horizontally 

 leads us, by means of the causal connection existing among all 

 natural phenomena, to the distribution of solids and fluids into 

 ihe continents and seas which constitute the upper crust of our 

 planet. We here touch upon a point of contact between geo- 

 logical and geographical geognosy which would constitute the 

 complete history of the form and extent of continents. The 

 limitation of the solid by the fluid parts of the earth's surface, 

 and their mutual relations of area, have varied very consider- 

 ably in the long series of geognostic epochs. They were very 

 different, for instance, when carboniferous strata were horizon- 

 tally deposited on the inclined beds of the mountain limestone 

 and old red sandstone ; when lias and oolite lay on a substra- 

 tum of keuper and muschelkalk, and the chalk rested on the 

 slopes of green sandstone and Jura limestone. If, with Elie 

 de Beaumont, we term the waters in which the Jura limestone 

 and chalk formed a soft deposit the Jurassic or oolitic, and the 

 cretaceous seas, the outlines of these formations will indicate, 

 for the two corresponding epochs, the boundaries between the 

 already dried land and the ocean in which these rocks were 

 forming. An ingenious attempt has been made to draw maps 

 of this physical portion of primitive geography, and we may 

 consider such diagrams as more correct than those of the wan- 

 derings of lo or the Homeric geography, since the latter are 

 merely graphic representations of mythical images, while the 

 former are based upon positive facts deduced from the science 

 of geology. 



The results of the investigations made regarding the areal 

 relations of the solid portions of our planet are as follows : in 

 the most ancient times, during the silurian and devonian tran- 

 sition epochs, and in the secondary formations, including the 

 trias, the continental portions of the earth were limited to in- 

 sular groups covered with vegetation ; these islands at a sub- 

 sequent period became united, giving rise to numerous lakes 

 and deeply-indented bays ; and, finally, when the -chains of 

 the Pyrenees, Apennines, and Carpathian Mountains were 

 elevated about the period of the more ancient tertiary forma 

 lions, large continents appeared, having almost their present 



