134 RELATIVE GEOLOGICAL ANTIQUITY OF TREES. 



visible througli the cloudy atmospliere. Dense valors arose 

 from the ocean, and fell in violent showers over the land, 

 returning back to that reservoir in ten thousand roaring 

 torrents. This period has been called by Agassiz the Age 

 of Fishes. There were neither reptiles, birds, nor mammals 

 then in existence. 



Toward the close of the Palasozoic period, the earth appears 

 to have presented the appearance of one vast archipelago, or 

 collection of islands, and vegetation was developed on the 

 grandest scale. It was during this epoch that the coal was 

 deposited, as only on the coasts of tropical islands could such 

 plants grow as are found fossil in the coal formation. The 

 vegetable remains are mostly found, not in the coal, but in 

 the accompanying clayey and sandy soil with which the coal 

 is interstratified. 



From these remains it can be proved that splendid forests 

 grew on the boggy soil of these islands. Here elevated itself 

 a tree fern, its summit penetrating the dark clouds which 

 obscured the heavens ; there, a gigantic -lycopodium or club 

 moss. Calamites and equisetaceee were abundant; and, in 

 addition to this, we find traces of coniferous plants, or plants 

 allied to the Fir tree, and resembling the Norfolk Island Pine, 

 {Araucaria excelsa.) Barren uniformity, however, marked 

 the character of these forests. Only seven hundred and fifty 

 plants are at present known to Naturalists, which were at this 

 time diffused over the whole earth; whilst to-day, in Europe, 

 one of the smallest dVisions of the earth, more than ten thou- 

 sand species are known. The earth at the time of the stone- 

 coal formation was yet too warm for the sun's rays to produce 

 any es&ential influence on the climatic conditions. The tem- 

 perature was pretty much the same all over the earth. Hence 

 the stone-coal plants are the same, although found in coun- 

 tries thousands of mUes apart. Even the poles of the earth 

 were covered with a tropical vegetation, although now cooled 

 down so as to be covered with a mantle of everlasting ice and 

 snow. This opinion has been advanced by some Naturalists ; 

 but as light is ntesary to the formation of plants, and as the 

 poles are deprived of its influence during a part of the 

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