On the upturned and denuded edges of the Silurian strata a great pile of contemporaneous volcanic rocks of Lower Old Red Sandstone age rests unconformably, which consists chiefly of lavas with thin partings of tuff. A striking feature is the absence of coarse sediments, thus indicating prolonged volcanic activity. They cover an area of about 230 sq. m. in the eastern part of the Cheviots and rise to a height of 2676 ft. above the sea. The lavas comprise dark pitchstone, resembling that at Kirk Yetholm, and porphyritic and amygdaloidal andesites and basalts. This volcanic platform is pierced by a mass of granite about 20 sq. m. in extent, which forms the highest peak in the Cheviot range. It has been described by Dr Teall as an augite-biotite-granite having strong affinities with the augite-bearing granitites of Laveline and Oberbrück in the Vosges. Both the granite and the surrounding lavas are traversed by dykes and sills of intermediate and acid types represented by mica-porphyrites and quartz-felsites.
On their north-west margin the Lower Old Red volcanic rocks are covered unconformably by the upper division of that system composed of red sandstones and conglomerates, which, when followed westwards, rest directly on the Silurian platform. Towards the south and east the volcanic pile is overlaid by Carboniferous strata, thus indicating a prolonged interval of denudation.
On the northern slopes of the western part of the Cheviots the representatives of the Cementstone group of the Carboniferous system come to the surface, where they consist of shales, clays, mudstones, sandstones with cementstones and occasional bands of marine limestone. These are followed in normal order by the Fell Sandstone group, comprising a succession of sandstones with intercalations of red and green clays and impure cementstone bands. They form the higher part of the Larriston Fells and are traceable eastwards to Peel Fell, where there is evidence of successive land surfaces in the form of dirt beds. They are succeeded by the Lewisburn coal-bearing group, which represents the Scremerston coals.
CHEVREUL, MICHEL EUGÈNE (1786–1889), French chemist, was born, on the 31st of August 1786, at Angers, where his father was a physician. At about the age of seventeen he went to Paris and entered L. N. Vauquelin’s chemical laboratory, afterwards becoming his assistant at the natural history museum in the Jardin des Plantes. In 1813 he was appointed professor of chemistry at the Lycée Charlemagne, and subsequently undertook the directorship of the Gobelins tapestry works, where he carried out his researches on colour contrasts (De la loi du contraste simultané des couleurs, 1839). In 1826 he became a member of the Academy of Sciences, and in the same year was elected a foreign member of the Royal Society of London, whose Copley medal he was awarded in 1857. He succeeded his master, Vauquelin, as professor of organic chemistry at the natural history museum in 1830, and thirty-three years later assumed its directorship also; this he relinquished in 1879, though he still retained his professorship. In 1886 the completion of his hundredth year was celebrated with public rejoicings; and after his death, which occurred in Paris on the 9th of April 1889, he was honoured with a public funeral. In 1901 a statue was erected to his memory in the museum with which he was connected for so many years. His scientific work covered a wide range, but his name is best known for the classical researches he carried out on animal fats, published in 1823 (Recherches sur les corps gras d’origine animale). These enabled him to elucidate the true nature of soap; he was also able to discover the composition of stearin and olein, and to isolate stearic and oleic acids, the names of which were invented by him. This work led to important improvements in the processes of candle-manufacture. Chevreul was a determined enemy of charlatanism in every form, and a complete sceptic as to the “scientific” psychical research or spiritualism which had begun in his time (see his De la baguette divinatoire, et des tables tournantes, 1864).
CHEVRON (Fr. from chévre, a goat), in architecture, the beams or rafters in the roofs of a building, meeting in an angle with a fancied resemblance to the horns of a butting goat; in heraldry a bent bar on a shield, used also as a distinguishing badge of rank on the sleeves of non-commissioned officers in most armies and navies and by police and other organized bodies wearing uniform, and as a mark of good conduct in the army and navy. Chevron is also an architectural term for an inflected ornament, called also “zig-zag,” found largely in romanesque architecture in France, England and Sicily. It is one of the most common decorations found in the voussoirs of the Norman arch, and was employed also on shafts, as in the cloisters of Monreale near Palermo, those of St Paul outside Rome, and many churches in Germany. Its earliest appearance was in the tomb of Agamemnon at Mycenae, where the shafts flanking the entrance doorway have nine decorative chevron bands; in this case there is no doubt it was derived from the metal casing of the early wood columns.
CHEVROTAIN, a name taken from the French to designate the various representatives of the mammalian ungulate family Tragulidae. These tiny animals, commonly known as mouse-deer, are in no wise nearly related to the true deer, but constitute by themselves a special section of artiodactyle ungulates known as Tragulina, for the characteristics of which see Artiodactyla. The typical genus Tragulus, which is Asiatic, contains the smallest representatives of the family, the animals having more of the general aspects and habits of some rodents, such as the agoutis, than of other ruminants. The longest-known species are T. javanicus, T. napu, T. kanchil, T. stanleyanus and T. memmina; but a number of other forms, best regarded for the most part as races, have been named. Of those mentioned, the first four are from the Malay Peninsula or the islands of the Indo-Malay Archipelago, the last from Ceylon and India. Kanchil and napu (or napoh) are the Malay names of the species with those specific titles. The second genus, Dorcatherium (or Hyomoschus), is African, and distinguished chiefly by the feet being stouter and shorter, the outer toes better developed, and the two middle metacarpals not welded together. Its dental formula (as that of Tragulus) is i.0, c.1, p.3, m.3 = 34. Vertebrae: C. 7, D. 13, L. 6, S. 5, Ca. 12-13. The only existing species, D. aquaticum (fig.), in type is rather larger than any of the Asiatic chevrotains, which it otherwise much resembles, but is said to frequent the banks of streams, and have much the habits of pigs. It is of a rich brown colour, with back and sides spotted and striped with white; and it is evidently the survivor of an ancient form, as remains of a species only differing in size (D. crassum) have been found in the Miocene deposits of France. For long this species was supposed to be restricted to West Africa, but it has recently been obtained in East Central Africa, where it is represented by a local race. (R. L.*)
CHEYENNE (Sioux for “of alien speech”), a tribe of North American Indians of Algonquian stock. They formerly lived on the Cheyenne river, North Dakota. Driven west by the Dakotas, they were found by early explorers at the eastern base of the Black Hills, South Dakota. Part of them later moved south and allied themselves with the Arapahoes. Their whole history has been one of war with their red and white neighbours. They are a powerful athletic race, mentally superior to the average American Indian. They are divided into eleven subdivisions and