GEOLOGY. 



the name Triassic, which means triple, from 

 being found in Germany in three distinct groups, 

 of which the first and third alone exist in 

 Britain. 



The system contains sandstones of different 

 colours, shales, and conglomerates ; but the dis- 

 tinguishing product is rock-salt. This occurs in 

 beds of from seventy to one hundred feet thick in 

 Cheshire, whence we obtain salt for daily con- 

 sumption. Salt-springs also abound in salt dis- 

 tricts, being formed by the issuing of water 

 through the salt rocks below. The Triassic 

 rocks are found in patches in the British 

 Isles, but extensively on the continent of 

 Europe and in America. 



Organic Remains. The organic remains 

 are very scanty, especially when compared 

 with the exuberance of life in eras before 

 and after. Plants are rare both in number 

 and species. We find horse-tails, calamites, 

 and ferns. The gigantic trees of the Coal- 

 measures no longer exist, and we have 

 instead short palm-like trees, like the modern 

 cycas. The vegetation is mostly of a trop- 

 ical kind. 



Animals are far from abundant, but are 

 more numerous than the plants. We have 

 no corals, and few encrinites, and bone- 

 plated fishes are rare. There are a few 

 shells, some crustaceans, and several great 

 shark-like fishes. Reptiles, however, are 

 numerous, and of gigantic size. One brute 

 in particular, called the Labyrintkodon^ from the 

 labyrinth-like structure of a section of its teeth, is 

 an uncouth, frog-like creature, with great staring 

 eyes, and immense toothed jaws. The most 

 abundant remains in the Triassic are the great 

 footprints of large lizards. These are found in 

 Scotland, but are so numerous in America, that 

 above one hundred species of creatures have been 

 distinguished, as indicated by these footprints. 

 Huge birds, too, were numerous, and have also 

 left their marks upon the rocks. These rocks 



VIII. OOLITIC OR JURASSIC SYSTEM. 



Description. We have now arrived at a 

 remarkable epoch, whose remains, abundant and 

 wonderful, have been more fully investigated and 

 described by celebrated men than perhaps any 

 other. The forms of life, habits, and scenery are 

 more like those of our own times, and can there- 

 fore be restored with the greater certainty. 



The term Oolitic is applied to a series of rocks 



Labyrinthodon. 



furnish the earliest evidences of warm-blooded 

 mammals. 



Scenery. The scenery of the old Triassic age 

 seems to have been peculiar, and we can form but 

 a dim notion regarding it. We can easily see that 

 the seas were shallow, with bordering lagoons, in 

 which the salt waters, were evaporated in the strong 

 sun-rays, and left the salt-beds that are now of such 

 service to us. By the muddy rivers lived great 

 crocodiles, that lurked amid the reeds and pines, 

 and fed on shell-fish and crustaceans, and left 

 their footprints on the yielding mud ; while on the 

 dry plains above, grew plants adapted for an arid 

 soil and tropical climate. 



' From Greek labyrinthot, a labyrinth, and odoui, odontos, a 

 tooth. 



Oolitic Plants : 

 i, Palm ; 2, Tree-fern ; 3, Cycas ; 4, Pandanus ; 5, Zamia. 



which in England form three distinct groups the 

 Lias, Oolite Proper, and Wealden. 



The Lias is the oldest, and receives its name, a 

 corruption of Hers or layers, from the thin varie- 

 gated beds of which the rocks are composed, and 

 which present a remarkable ribbon-like appear- 

 ance not easily forgotten. The Oolite 1 is above 

 the Lias, and is so called from the rock being 

 greatly composed of small round grains like the 

 eggs of the cod, so that it signifies the egg-rock. 

 It is also called roe-stone and pea-stone, according 

 to the size of the particles. These strange gran- 

 ules consist almost entirely of lime or grains of 

 sand coated with lime. The Wealden is the 

 highest rock in the series, and receives its name 

 from being developed largely in the Weald in 

 Kent and Sussex. The name Oolitic has been 

 applied to the whole system, because the egg- 

 structure is common to all the rocks in the series ; 

 the term Jurassic, from its being largely found in 

 Mount Jura, is also given to it. 



The Oolitic system consists of a series of sand- 

 stones, limestones (sometimes so hard as to be 

 used as marble), shales, and clays, while ironstone 

 bands, coal, lignite, and jet are abundant. The 

 sandstones are useful as building-stone, the cele- 

 brated Bath and Portland stones, so much used 

 in London and the south of England, being 

 varieties. The limestones are burned for agri- 

 cultural purposes ; the clays are extensively devel- 

 oped, and receive different names in different 

 parts, and yield alum, sulphur, and fuller's-earth. 

 Ironstone is abundant and good, and furnishes 

 a great part of the iron of Yorkshire, being eleven 

 feet thick. The coal is workable and abundant, 

 which disproves the notion, too prevalent, that coal 

 can be obtained only from the Coal-measures. 



1 From Greek Son, an egg, and litkat, a stone. 



