40 DEVONIAN ERA. 



proof of the more equable diffusion of a tropical climate in 

 ancient times, and distinctly attributes it to the action of the 

 internal heat of the earth. The early animals are not so uni- 

 form over large geographical areas as the plants. M. Agassiz 

 surmises, from an examination of the fishes of the ancient seas, 

 that the ocean did not at first contain much salt, but gradually 

 acquired its present infusion of that material ; a theory, it 

 may be remarked, which derives support from the suggestion, 

 that the salt of the sea has been mainly brought thither, in the 

 course of time, by rivers, washing it in particles out of the 

 land, in common with other detritus, while it is obvious that 

 rain does not restore it.( 22 ) It is easy to suppose a compara- 

 tive absence of salt in the early ocean affecting animal and 

 vegetable marine life in different ways and degrees. 



As yet overlooking possible exceptions of a narrow and 

 dubious kind ( 23 ) we meet with no traces of land plants : 

 remains of terrestrial animals have not even been suspected. 

 This exclusively marine character of the flora and fauna of the 

 early ages is usually thought to betoken the non-existence of 

 dry land. But there are reasons apart from the fossil history 

 for believing that great masses had been exposed to the atmo- 

 sphere in those ages. The earliest strata give token of vast 

 disintegration. In our time, this process is usually seen tak- 

 ing place chiefly in the atmosphere, and at the point where 

 land and water meet ; in a much less activity below the sur- 

 face of the ocean. It would thus appear likely that there was 

 dry land in the eras of the earliest stratified formations, 

 though, from whatever cause, it bore no vegetation and sus- 

 tained no animals, or was only a scene of life in certain rare 

 and favourably situated places. The ages of mountains, from 

 which this inference is derived, form one of the most curious 

 as well, as trustworthy chapters in geological science. It is 

 as certain that the Grampian mountains of Scotland are older 

 than the Alps and Apennines, as it is that civilization had 

 visited Italy, and had enabled her to subdue the world, while 

 Scotland was the residence of " roving barbarians." The 

 Pyrenees, Carpathians, and other ranges of continental 



