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with sea water. Crystals of zeolites (phillipsite) form in the red-clay as radiate, nodular groups. Lumps of manganese oxide, with a black, shining outer surface, are also characteristic of this deposit, and frequently encrust pieces of pumice or animal remains. The only fossils of the clay are radiolaria, sharks’ teeth and the ear-bones of whales, precisely those parts of the skeleton of marine creatures which are hardest and can longest survive exposure to sea-water. Their comparative abundance shows how slowly the clay gathers. Small rounded spherules of iron, believed by some to be meteoric dust, have also been obtained in some numbers. Among the rocks of the continents nothing exactly the same as this remarkable deposit is known to occur, though fine dark clays, with manganese nodules, are found in many localities, accompanied by other rocks which indicate deep-water conditions of deposit.

Another type of red-clay is found in caves, and is known as cave-earth or red-earth (terra rossa). It is fine, tenacious and bright red, and represents the insoluble and thoroughly weathered impurities which are left behind when the calcareous matter is removed in solution by carbonated waters. Similar residual clays sometimes occur on the surface of areas of limestone in hollows and fissures formed by weathering.

Boulder-clay is a coarse unstratified deposit of fine clay, with more or less sand, and boulders of various sizes, the latter usually marked with glacial striations.

Some clay rocks which have been laid down by water are very uniform through their whole thickness, and are called mud-stones. Others split readily into fine leaflets or laminae parallel to their bedding, and this structure is accentuated by the presence of films of other materials, such as sand or vegetable debris. Laminated clays of this sort are generally known as shales; they occur in many formations but are very common in the Carboniferous. Some of them contain much organic debris, and when distilled yield paraffin oil, wax, compounds of ammonia, &c. In these oil-shales there are clear, globular, yellow bodies which seem to be resinous. It has been suggested that the admixture of large quantities of decomposed fresh-water algae among the original mud is the origin of the paraffins. In New South Wales, Scotland and several parts of America such oil-shales are worked on a commercial scale. Many shales contain great numbers of ovoid or rounded septarian nodules of clay ironstone. Others are rich in pyrites, which, on oxidation, produces sulphuric acid; this attacks the aluminous silicates of the clay and forms aluminium sulphate (alum shales). The lias shales of Whitby contain blocks of semi-mineralized wood, or jet, which is black with a resinous lustre, and a fibrous structure. The laminated structure of shales, though partly due to successive very thin sheets of deposit, is certainly dependent also on the vertical pressure exerted by masses of super-incumbent rock; it indicates a transition to the fissile character of clay slates.  (J. S. F.) 

CLAY CROSS, an urban district in the Chesterfield parliamentary division of Derbyshire, England, near the river Amber, on the Midland railway, 5 m. S. of Chesterfield. Pop. (1901) 8358. The Clay Cross Colliery and Ironworks Company, whose mines were for a time leased by George Stephenson, employ a great number of hands.

CLAYMORE (from the Gaelic claidheamh mòr, “great sword”), the old two-edged broadsword with cross hilt, of which the guards were usually turned down, used by the Highlanders of Scotland. The name is also wrongly applied to the single-edged basket-hilted sword adopted in the 16th century and still worn as the full-dress sword in the Highland regiments of the British army.

CLAYS, PAUL JEAN (1819–1900), Belgian artist, was born at Bruges in 1819, and died at Brussels in 1900. He was one of the most esteemed marine painters of his time, and early in his career he substituted a sincere study of nature for the extravagant and artificial conventionality of most of his predecessors. When he began to paint, the sea was considered by continental artists as worth representing only under its most tempestuous aspects. Artists cared only for the stirring drama of storm and wreck, and they clung still to the old-world tradition of the romantic school. Clays was the first to appreciate the beauty of calm waters reflecting the slow procession of clouds, the glories of sunset illuminating the sails of ships or gilding the tarred sides of heavy fishing-boats. He painted the peaceful life of rivers, the poetry of wide estuaries, the regulated stir of roadsteads and ports. And while he thus broke away from old traditions he also threw off the trammels imposed on him by his master, the marine painter Theodore Gudin (1802–1880). Endeavouring only to give truthful expression to the nature that delighted his eyes, he sought to render the limpid salt atmosphere, the weight of waters, the transparence of moist horizons, the gem-like sparkle of the sky. A Fleming in his feeling for colour, he set his palette with clean strong hues, and their powerful harmonies were in striking contrast with the rusty, smoky tones then in favour. If he was not a “luminist” in the modern use of the word, he deserves at any rate to be classed with the founders of the modern naturalistic school. This conscientious and healthy interpretation, to which the artist remained faithful, without any important change, to the end of an unusually long and laborious career, attracted those minds which aspired to be bold, and won over those which were moderate. Clays soon took his place among the most famous Belgian painters of his generation, and his pictures, sold at high prices, are to be seen in most public and private galleries. We may mention, among others, “The Beach at Ault,” “Boats in a Dutch Port,” and “Dutch Boats in the Flushing Roads,” the last in the National Gallery, London. In the Brussels gallery are “The Port of Antwerp,” “Coast near Ostend,” and a “Calm on the Scheldt”; in the Antwerp museum, “The Meuse at Dordrecht”; in the Pinakothek at Munich, “The Open North Sea”; in the Metropolitan Museum of Fine Arts, New York, “The Festival of the Freedom of the Scheldt at Antwerp in 1863”; in the palace of the king of the Belgians, “Arrival of Queen Victoria at Ostend in 1857”; in the Bruges academy, “Port of Feirugudo, Portugal.” Clays was a member of several Academies, Belgian and foreign, and of the Order of Leopold, the Legion of Honour, &c.

See Camille Lemonnier, Histoire des Beaux-Arts (Brussels, 1887).  (O. M.*) 

CLAYTON, JOHN MIDDLETON (1796–1856), American politician, was born in Dagsborough, Sussex county, Delaware, on the 24th of July 1796. He came of an old Quaker family long prominent in the political history of Delaware. He graduated at Yale in 1815, and in 1819 began to practise law at Dover, Delaware, where for a time he was associated with his cousin, Thomas Clayton (1778–1854), subsequently a United States senator and chief-justice of the state. He soon gained a large practice. He became a member of the state House of Representatives in 1824, and from December 1826 to October 1828 was secretary of state of Delaware. In 1829, by a combination of anti-Jackson forces in the state legislature, he was elected to the United States Senate. Here his great oratorical gifts gave him a high place as one of the ablest and most eloquent opponents of the administration. In 1831 he was a member of the Delaware constitutional convention, and in 1835 he was returned to the Senate as a Whig, but resigned in the following year. In 1837–1839 he was chief justice of Delaware. In 1845 he again entered the Senate, where he opposed the annexation of Texas and the Mexican War, but advocated the active prosecution of the latter once it was begun. In March 1849 he became secretary of state in the cabinet of President Zachary Taylor, to whose nomination and election his influence had contributed. His brief tenure of the state portfolio, which terminated on the 22nd of July 1850, soon after Taylor’s death, was notable chiefly for the negotiation with the British minister, Sir Henry Lytton Bulwer, of the Clayton-Bulwer Treaty (q.v.). He was once more a member of the Senate from March 1853 until his death at Dover, Delaware, on the 9th of November 1856. By his contemporaries Clayton was considered one of the ablest debaters and orators in the Senate.

See the memoir by Joseph P. Comegys in the Papers of the Historical Society of Delaware, No. 4 (Wilmington, 1882).