440 MESOZOIC TIME — REPTILIAN AGE. 



below, which might ultimate in fractures, especially about the 

 axis of the depression. The tilting, fractures, joints, and ejec- 

 tions of igneous rock are, therefore, parts of one connected series 

 of events. 



The manner in which the trap at its eruption has sometimes 

 separated the layers of sandstone, and in this way escaped to the 

 surface, instead of coming up through the fissures simply, shows 

 that the rock had been tilted extensively before the ejection; and, 

 as the trap dikes intersect the later beds of the formation, the 

 igneous ejections were among the later results of the period, if not 

 to a great extent subsequent in time. 



It is hence no mystery that rocks of igneous origin are intimately 

 associated with rocks of aqueous origin in these Triassic regions. 



Thus the period of these rocks came to a close somewhat similar 

 to that of the Carboniferous age. The Carboniferous age ended 

 in a period of disturbance, escape of heat, as shown in consolida- 

 tions and metamorphism, and a complete destruction of life along 

 the Continental border ; and the period of these sandstones was 

 closed in uplifts, fractures, emissions of heat, consolidations, and 

 destructions of life. But in the former case the crust was yield- 

 ing, and became folded into mountains : in the latter, the action, 

 though ranging along the same line of coast, from South Carolina to 

 Newfoundland, was more limited ; the stiffened crust only yielded 

 by breaking ; the heat came out in ejected melted rock, instead of 

 a slow, gentle effusion, and the swelling up of the lava and simple 

 tiltings of the strata formed hills and ridges. The destruction 

 of life was in both cases complete. 



Life of the Period. — The steps of progress in the life of the globe, 

 as the Mesozoic era opened in the Triassic period, were especially 

 important. The storing away as coal of the excess of atmospheric 

 carbon had purified the atmosphere; and soon after the close of 

 Palaeozoic time — whose great feature was that its animal life had 

 made rocks, and its plants, coal — we find higher races breathing 

 the better air. Saurians become numerous ; and the vertebrate 

 type expands by the appearance of the new classes Birds and 

 Mammals. Among these types, the Saurian continues rapidly to 

 rise in perfection with the following period of the age ; while the 

 birds and mammals remain of inferior types, forerunners of an 

 age of higher progress. 



Geography. — The position of the Triassic beds on the Atlantic 

 border shows that this part of the continent stood nearly at its 

 present level. The strange absence of Atlantic sea-shore deposits 

 in the Triassic period may be accounted for by supposing that the 



