76 STATE. OF THE SURFACE OF THE GLOBE 



oldest sedimentary strata of the transition formation, as is 

 indeed shewn by the effects of their metamorphic action. 

 Where knowledge cannot be obtained from direct evidence, 

 it may well be permitted, after a careful comparison of the 

 facts which are accessible, to take analogy as our guide, and 

 to advance a conjecture which would restore to the old gra- 

 nite a part of its disputed claim to the title of primordial 

 rock. 



The recent progress of geology, and the extended know- 

 ledge of geological epochs, characterised and determined by 

 the mineralogical composition of rocks, by the peculiarities 

 and succession of the organic remains which they contain, 

 and by the circumstances of their stratification, whether 

 uplifted, inclined, or with its horizontality undisturbed, 

 conduct us, pursuing the intimate causal connection of 

 phenomena, to the distribution of the solid and liquid por- 

 tions of the surface of our planet, its continents and seas. 

 We here indicate a connecting point between the history of 

 the revolutions which the globe has undergone, and the de- 

 scription of its present surface ; between geology and phy- 

 sical geography, which are thus combined in the general 

 consideration of the form and extent of continents. The 

 boundaries which separate the dry land from the liquid 

 element, and the relative areas of each, have varied greatly 

 during the long series of geological epochs ; they have been 

 very different, for example, when the strata of the coal for- 

 mation were deposited horizontally upon the inclined strata 

 of the mountain limestone and the old red sandstone; when 

 the lias and the oolite were deposited on the keuper and the 

 muschelkalk ; and when the chalk was precipitated on the 

 elopes of the greensand and oolitic limestone. If, with 



