THIRD PALEOZOIC PERIOD. 



those of the tropics at present, and were uniformly distributed 

 over all latitudes to which geological observations have been 

 extended, from the line to latitude 69, from which it is inferred, 

 that during this period the temperature of the earth was every- 

 where tropical, and everywhere uniform. 



273. The outlines of land and water were not materially dif- 

 ferent from those of the first period. It is probable, however, 

 that the seas retired from a portion of the central part of Brittany, 

 and advanced eastward, as well in Wales as in Cumberland, 

 leaving in the west a larger portion of uncovered land. They 

 extended, probably without interruption, from Europe to America, 

 covered a great part of North and South America, as well as all 

 that part of Europe which extended from Spain to the line of 

 direction now occupied by the Ural mountains. 



274. An examination of the Silurian strata has enabled 

 M. Elie de Beaumont to trace an approximate sketch of the 

 outlines of land and water in Western Europe, from which the 

 map given in fig. 142 was drawn. 



It appears from this, that there existed at this time two granitic 

 tracts, one between Brest and St. Malo, and the other between 

 Brest and Poitiers; the former having the direction of the 

 Finistere, and the latter of the Horbihan system, a neck of land 

 connecting them having the direction of the Longmynd system. 

 These probably, therefore, owed their elevation to the three con- 

 vulsions which produced these ranges severally. Other tracts of 

 land existed in Cornwall, in Scotland, and in Sweden, as shown 

 in the map, having the direction of the systems of Finistdre and 

 Longmynd. The granitic plateaux which include the Limousin 

 and Auvergne were also then above the waters, and were con- 

 nected with a much larger tract, extending from Toulon to 

 Innspruck. This second Palaeozoic period appears to have been 

 terminated by the effects of the geological disruption which 

 produced the Hundsruck system of M. Elie de Beaumont (209). 



THIRD PALEOZOIC PERIOD. 



275. After an interval of tranquillity as before the land being 

 divided from the waters the earth was repeopled with new tribes 

 and clothed with new vegetation. The strata deposited during 

 this third palaeozoic period have been denominated by Sir R. 

 Murchison, Devonian, from the circumstance of their prevalence 

 in that county. The principal mineralogical characteristic of the 

 Devonian stage is the old red sandstone. 



276. The animal world, now called into life, consisted, so far as 



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