FIRST PALAEOZOIC PERIOD. 



have been already explained, that during each of the five suc- 

 cessive periods the earth consisted, as at present, of continents 

 and seas ; that the continents were clothed with vegetation ; that 

 the seas were peopled by various marine tribes, some living at 

 parts of great depth, some near the coasts, and others upon the 

 shores between high and low water-mark ; and that even the 

 crust of the earth was subject to the same gradual oscillations 

 which are observed to exist at present in the north of Europe 

 and in other parts of the globe. 



258. The existence of a vegetable kingdom in each of the five 

 Palaeozoic periods is proved by the presence of coal in all the 

 stages. That mineral is worked in Portugal in the Silurian 

 stage. In Spain its richest mines are in the Devonian stage, 

 and in Saxony it is worked in the Permian stage. These facts 

 show, that though the coal-fields are by far most prevalent in 

 the Carboniferous, the other Palaeozoic stages furnish their share 

 of that mineral to industry and the arts. 



Having thus taken a general view of the Palaeozoic age, con- 

 sidering its periods collectively, we shall now briefly notice the 

 most remarkable circumstances attending these periods severally. 



FIEST PALAEOZOIC PERIOD. 



259. The first Palaeozoic stage includes the group of strata of 

 which the Cambrian system of Sedgwick and the lower Silurian 

 system of Murchison are composed. It appears from an exami- 

 nation of the strata, more especially those observed in North and 

 South America and Bohemia, that a considerable time must have 

 elapsed between the epoch at which this stage began to be 

 deposited on the subjacent Azoic rocks, and the commencement of 

 the animalisation of the globe. Strata of immense thickness are 

 everywhere found between the superior surface of the Azoic rocks 

 and the first layers of organic remains, the formation of which, 

 according to all the known laws of sedimentary deposits, must have 

 occupied a great lapse of time. That these were deposited from 

 waters which had a temperature too elevated to allow of organic 

 life, is in the highest degree probable ; and it must be inferred 

 that the creation of an animal and vegetable kingdom, or a fauna 

 and flora, as they are called, was postponed until the temperature 

 of the globe had fallen to a point not much above that of the 

 present tropics. 



260. During this first Palaeozoic or Cambrian period the waters 

 of the ocean covered all that part of Europe extending from Spain 

 to the Ural mountains, as well as a great part of North and 

 South America. The shores of these seas can be traced, by the 



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