In the early years of the 19th century a great controversy convulsed the geological world as to the origin of the older basalts or "floetz-traps." Werner, the Saxon mineralogist, and his school held them to be of aqueous origin, the chemical precipitates deposited in primeval seas, but Hutton and a number of French geologists maintained that they were really volcanic rocks emitted by craters now extinct (see Geology: Historical).
Of the less common minerals of basalt, a few may be mentioned. Black hornblende, dark brown in thin sections, and often corroded, is not uncommon, especially in intrusive basalts. Hypersthene occurs also, usually replacing olivine. Black mica (biotite) is not infrequently to be seen. Sapphire, garnet and zircon are rare. Minerals of the felspathoid group occur in a large number of basaltic rocks; nepheline and leucite are the most common, but haüyne is occasionally present. If nepheline entirely replaces felspar, the rock is known as nepheline-basalt; if the replacement is only partial the term nepheline-basanite is used. Similarly there are leucite-basalts and leucite-basanites. The nepheline is in small six-sized prisms, and usually cannot be detected with the unaided eye. Even with the help of the microscope nepheline basalts are not always easy to determine, as the crystals may be exceedingly small and imperfect, and they readily decompose into analcite and zeolites. In some cases only the presence of an anisotropic substance, with weak double refraction and readily attacked by acids (the so-called "nephelinitoid"), can be made out. This substance may be imperfectly crystallized nepheline, or a peculiar glass which is rich in soda. Most nepheline basalts are fine grained, very dark coloured rocks, and belong to the Tertiary period. They are fairly common in some parts of Germany and occur also in Tripoli, Asia Minor, Montana, Cape Verde Islands, &c. Leucite-basalts contain small rounded crystals of leucite in place of plagioclase felspar. Rocks of this group are well known in the Eifel, and other volcanic districts in Germany, also in Bohemia, Italy, Java, Montana, Celebes, &c. The minerals haüyne, nosean, sodalite and melilite tend to occur with some frequency in nepheline and leucite-basalts, though rare in ordinary basalts. Melilite, a lime-alumina-silicate, is characteristic of certain very basic rocks, the melilite-basalts. It is pale yellow or colourless in thin sections, and yields peculiar and characteristic dark blue polarization colours. This rare group of rocks is known to occur in Bohemia, Swabia and South Africa. Perofskite, in small dark brown cubic crystals, is a constant accessory in these rocks. The augite is usually violet coloured, and shows zonal and hour-glass structures. Green augite may occur in the nepheline-basalts, and aegerine (soda-iron-augite) is occasionally found in them.
The distribution of basalts is world-wide; and in some places
they occur in immense masses, and cover great areas. In Washington, Oregon, and Idaho many thousands of square miles are occupied by basaltic-lava flows. In the Sandwich Islands and Iceland they are the prevalent lavas; and the well-known columnar jointed basalts of Skye, Staffa, and Antrim (Giant's Causeway) form a southward extension of the Icelandic volcanic province, with which they are connected by the similar rocks of the Faeroe Islands. In the Deccan in India great basaltic lava fields are known; and Etna and Vesuvius emit basaltic rocks. In older geological periods they were not less common; for example, in the Carboniferous in Scotland.
(J. S. F.)
BASCOM, JOHN (1827- ), American educationalist and philosophical writer, was born at Genoa, New York, on the 1st of May 1827. He graduated at Williams College in 1849 and at the Andover Theological Seminary in 1855, was professor of rhetoric at Williams College from 1855 to 1874, and was president of the University of Wisconsin and professor of mental and moral philosophy there from 1874 to 1887. In 1887-1891 and in 1901-1903 he was lecturer in sociology, and in 1891-1901 professor of economics in Williams College. He retired in 1903. Among his publications may be mentioned: Aesthetics (1862); Philosophy of Rhetoric (1865); Science, Philosophy and Religion (1871); Philosophy of English Literature (1874); Philosophy of Religions (1876); Problems in Philosophy (1885); The New Theology (1891); Social Theory (1895); Evolution and Religion (1896); Growth of Nationality in the United States (1899); and God and His Goodness (1901).
BASE. (1) (Fr. bas, Late Lat. bassus, low; cf. Gr. βαθύς) an adjective meaning low or deep, and so mean, worthless, or wicked. This sense of the word has sometimes affected the next, which is really distinct. (2) (Gr. βάσις, strictly "stepping," and so a foundation or pedestal) a term for a foundation or starting point, used in various senses; in sports, e.g. hockey and baseball; in geometry, the line or face on which a figure or solid stands; in crystallography, e.g. "basal plane"; in surveying, in the "base line," an accurately measured distance between the points from which the survey is conducted; in heraldry, in the phrase "in base," applied to any figure or emblem placed in the lowest part of a shield.
In chemistry the term denotes a substance which combines with an acid to form a salt. In inorganic chemistry such compounds are almost invariably oxides or hydroxides, and water in eliminated during the combination; but in organic chemistry many compounds exist, especially ammonia derivatives, which directly combine with acids. Chemical bases are consequently antithetical to acids; and an acid is neutralized by a base with the production of a salt. They reverse certain colour reactions of acids, e.g. turn red litmus blue; this is termed an "alkaline reaction."
In architecture the "base" is the lowest member of a column or shaft. In Egyptian and Greek architecture it is the raised slab in stone or cement on which the primitive timber column was placed, to keep it dry. Afterwards it was always reproduced in Egypt, even although the column, being in stone, no longer required it; a custom probably retained because, being of a much larger circumference than the lower part of the column, it gave increased stability. In Assyrian architecture, where it served to carry wooden posts or columns, it took the form of a large torus moulding with enrichments. In Persian architecture the base was much higher than in any other style, and was elaborately carved. In primitive Greek work the base consisted of the stone plinth as found in Crete and Tiryns, and of three small steps at Mycenae. In archaic Greek work it has already disappeared in the Doric order, but in the Ionic and Corinthian orders it is more or less richly moulded, the most elaborate examples being those found in the temple of Apollo at Branchidae in Milesia. For the contour of the mouldings see Orders. The Roman orders all have the favourite design known as the Attic base. Romanesque bases were rude but vigorous copies of the old classic base, and were often decorated with projections or spurs (Fr. griffes) at the angles of the square dies, thus connecting them with the square base. In the Early English style, these spurs followed the conventional design of the period, and about the same time the mouldings were deeply sunk and occasionally cut downwards, so that they would have held water if used externally. Later, the base becomes less bold in treatment, but much more complex in its contours, and in the 15th century is given an unusual height with two stages, the lower one constituting a kind of plinth, which is sometimes known as the ground table, or the base course.
A Base Court (Fr. basse cour, i.e. the lower court), is the first open space within the gates of a castle. It was used for exercising cavalry, and keeping live stock during a siege. (See Enceinte).