396 PICTURESQUE SKETCHES 



early, if not the very earliest, period of the earth's 

 history, there was great uniformity of general cha- 

 racter amongst the various animals whose remains 

 occur in rocks of the same age, over almost the whole 

 world, throughout a -vast thickness of deposit. But 

 there are no distinct indications of any other condi- 

 tions having then existed than might even now obtain, 

 with certain very trifling modifications, in some dis- 

 tricts, either of the northern or southern hemispheres. 



We have not yet, in these old rocks, obtained any 

 proof of the vicinity of land; and even the absence 

 of fishes, or their great rarity, although an important 

 negative fact, must not be assumed to prove abso- 

 lutely that no fishes existed at that time. Animals 

 of this kind may have abounded in other parts of the 

 sea, although the districts where we now find the 

 older fossiliferous deposits were possibly unfit, through 

 local conditions, for supplying their wants. 



Thirdly, That in the next succeeding period, when 

 fishes were very abundant and of extraordinary form, 

 and where there is also distinct proof, in the presence 

 of coal, of the existence of land near many of those 

 parts of the earth which are now occupied by the 

 deposits of this age, we are not obliged to suppose 

 that the land or coast-line was very extensive, that it 

 was everywhere unpeopled by quadrupeds and rep- 

 tiles, or that, even if such was the case, it possessed a 

 different atmosphere, or a very greatly increased tem- 

 perature. The parts of the world now most abound- 

 ing in vegetable life are not those in which animal 

 remains would most frequently be deposited; and 

 those containing the most nearly allied vegetable 

 forms are neither tropical in climate, nor are they 



