The same name is applied to sandstones of similar age which are found in Prince Edward island and Nova Scotia, in the valley of the Connecticut, and in New Jersey, Pennsylvania, Virginia, and North Carolina. To this series belong the coal fields of Richmond, Va., and Chatham, N. C. It is not improbable that these beds may include strata belonging to the subsequent or Jurassic period, so named because it is greatly developed in the Jura mountains. This includes both the lias and the oolite of England, which two on the continent are connected by beds of passage known as the Koessen or Rhaetic strata. The oolite of England consists of highly fossiliferous strata, chiefly marine, but in part fresh-water deposits, and through the Neocomian (Neufchatel) beds passes into the cretaceous or chalk formation, the upper part of which is characterized in northern Europe by that pure uncrystal-line limestone known as the chalk, a deep-sea deposit many hundred feet in thickness, made up almost entirely of the remains of minute animal organisms.-The rocks of the cenozoic or tertiary period are closely connected with the present time, and even in their lower portions contain some species of fossil shells identical with those now living.

Lyell has conveniently divided the tertiary, in ascending order, into eocene, miocene, and pliocene; to these are added a postpliocene division which includes the period of glacial drift. (See Diluvium.) The tertiary rocks attained a great thickness in some parts of their distribution. Thus in the Alps the miocene sandstones and conglomerates, known as the molasse, have in parts a thickness of more than 6,000 ft., while the nummulitic limestone, a subdivision belonging to the base of the tertiary, attains in the Mediterranean basin a thickness of more than 2,000 ft-We have already spoken of the trias of the eastern part of North America. The cretaceous is also represented in New Jersey and along the southern border of the palaeozoic from Georgia to Tennessee. Triassic, Jurassic, and cretaceous rocks are also widely spread between the Mississippi and the Rocky mountains, from Texas to Dakota, and westward over large areas to the Pacific coast. Deposits like the English chalk are unknown in this formation in North America. Tertiary rocks of various ages skirt the Atlantic coast from the Rio Grande to New Jersey, and are even met with off the coast of Massachusetts. They stretch from the gulf of Mexico to Kentucky, and like the mesozoic rocks occupy large areas to the westward, where on the Pacific coast they attain great thickness.-The succession of organic life in these various groups constitutes a study by itself, which will be considered under the head of Palaeontology. The palaeozoic age is preeminently the period of mollusks, corals,, and crustaceans, the most important class of which last in the early times were the trilo-bites, which appear in their greatest development in the Cambrian and Silurian, and die out in the carboniferous.

Fishes, the earliest representatives of vertebrate life, make their appearance near the summit of the Silurian, and abound in the upper palaeozoic; reptiles first appear in the carboniferous, and reach their greatest development in the mesozoic, in which reptilian forms of immense dimensions, and having curious resemblances to birds, are met with; while the birds themselves, which then first appeared, had remarkable reptilian affinities. The earliest evidences of mammals appear in the trias; throughout the niesozoic they were insignificant in size, and chiefly marsupial. In the eocene and miocene divisions of the tertiary we find the greatest development of mammalian forms. The deposits of these strata to the west of the Mississippi have within the last few years afforded a great number of remarkable species of mammals, which have been described by Leidy, Marsh, and Cope. The flora of the tertiary period is not less remarkable than its fauna. The geographical and climatic conditions of the northern hemisphere were then widely different from those of the present day.

Not only over Europe, but in North America, and northward as far as Greenland and Spitzbergen, a mild and equable climate prevailed, and the abundant plant remains preserved in the tertiary beds of those arctic regions show a luxuriant vegetation like that of the warmer parts of the temperate zone of to-day. This condition of things had been of long continuance; for in western America great beds of coal or lignite are found both in the cretaceous and the eocene strata. It was continued far into the pliocene; but as this went on, a cold climate like that which now characterizes the northern hemisphere prevailed, and gave rise to the glacial phenomena which have been described under the head of Diluvium. This change of climate is one of the most perplexing problems of geology. That a different distribution of land and water and of the oceanic currents may have contributed in some degree to this former climatic condition of the arctic regions is probable. Astronomical conditions connected with changes in the eccentricity of the earth's orbit have also been suggested as a cause; and finally it has been supposed that a somewhat different chemical composition of the earth's atmosphere prevailing up to that time may have cooperated with geographical conditions to maintain the peculiarly mild climate which, so far as we can judge, prevailed throughout the arctic regions in palaeozoic times, and perhaps without interruption nearly to the close of the tertiary.-The distribution of metallic ores and other economic materials in the various geological series is a point of much interest, and demands a brief notice in this place, although the subject is discussed more in detail under Mineral Veins, and in the articles on the different metals.

Metallic ores are met with both in beds interstratified with the rocky layers and in veins cutting these. The eozoie rocks are remarkable for their great deposits of crystalline iron ores, of which those of the Laurentian on Lake Champlain and those of the Huronian on Lake Superior are remarkable examples, as are also those of Missouri. Similar deposits occur in the eozoie rocks of Scandinavia and Russia. It is in these rocks also that titanic and chromic iron and emery occur; and to them belong graphite and beds of iron pyrites and copper pyrites, often associated with gold and with silver. Oxide of tin also appears to be characteristic of these crystalline rocks. These various ores are found not only in contemporaneous layers, but also in veins and beds cutting the crystalline strata. But the metallic ores are not confined to these more ancient rocks, for beds of oxide and carbonate of iron are met with at various horizons from the Cambrian up to recent times, while under the heads of Coppek-and Gold the distribution of those metals and their ores is described.