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# 1911 Encyclopædia Britannica/Tetrahedrite

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​TETRAHEDRITE, a mineral consisting typically of copper sulph-autimonite, Cu$_3$SbS$_3$, but often of complex composition. The copper is usually isomorphously replaced by variable amounts of silver, iron, zinc, mercury, lead or cobalt, and the antimony by arsenic or bismuth. In general, the formula is R′$_6$X$_2$S$_6$+xR″$_6$X$_2$S$_9$, where R′=Cu, Ag; X= Sb, As, Bi; R″=Fe, Zn, and x is a small fraction, often 1/10 or 1/5 . Numerous special names have been applied to varieties differing in chemical composition; the arsenic compound, Cu$_3$AsS$_3$, , is known as tennantite (after Smithson Tennant). The old German name Fahlerz includes both tetrahedrite and tennantite, and so does the term “grey copper ore” of miners. Tefrahcdrite is an important ore of copper, the formula Cu$_3$SbS$_3$, corresponding with 57.5 per cent. of this metal; it is also largely worked as an ore of silver, of which element it sometimes contains as much as 30 per cent. Well-developed crystals are of frequent occurrence; they belong to the tetrahedral class of the cubic system, and their tetrahedral form is a very characteristic feature of the mineral, which forthis reason was named tetrahedrite. Fig. 1
| Fig. 1. | Fig. 2. |
| Crystals of Tetrahedrite. ||
shows a combination of a tetrahedron and a triakis-tetrahedron {211}, and fig. 2 a tetrahedron with the rhombic dodecahedron. Interpenetrating twinned crystals sometimes occur. The colour is steel-grey to iron-black, and the lustre metallic and brilliant. The streak is usually black; sometimes, however, it is dark cherry-red, and very thin splinters of the mineral then transmit a small amount of blood-red light. The hardness is 41/2, and the specific gravity varies with the composition from 4.4 to 5.1. There is no cleavage, and the fracture is conchoidal. The material is often very impure owing to intimate intermixture with chalcopyrite.
Tetrahedrite occurs in metalliferous veins associated with chalcopyrite, pyrites, blende, galena, &c. Fine groups of crystals, coated on their surface with brassy or brilliantly tarnished chalcop rite, were formerly found at Herodsfoot mine, near Liskeard in Cornwall. Good crystals are also met with at Kapnik-Banya in' Hungary, in the Harz, Peru, and other places. Tennantite occurs as small crystals of cubic or dodecahedral habit in many ​Cornish copper mines, especially in the neighbourhood of Redruth: it is also found as small, brilliant crystals very rich in faces in the white crystalline dolomite of the Binnenthal in the Valais, Switzerland, and under the name binnite was long considered as a distinct species. (L. J. S.)
# 1911 Encyclopædia Britannica/Tetrastoön

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​TETRASTOÖN (Gr. τέτρα-, four, and στοά, a portico), the term in architecture given to a rectangular court round which on all four sides is carried a covered portico or colonnade; the same as peristyle (q.v.).
# 1911 Encyclopædia Britannica/Tetragrammaton

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​TETRAGRAMMATON (τέτταρα, four; γράμμα, letter), a Greek compound, found in Philo and Josephus, which designates the divine name composed of the four Hebrew letters J H V H (יהוה). The derivation and pronunciation of the Tetragrammaton is still doubtful. The form Jehovah (q.v.) used in some of the English Versions is an error which arose in the 16th century. It is now generally assumed that the word is the causative form (hiph‛il) and should be pronounced Yahveh or Yahweh (accent on second syllable). The Jews quite early ceased to pronounce the tetragrammaton, substituting (as the Books of Chronicles and the LXX translation already indicate) the word Lord (’Adonai). The priests continued to use the name in the Benediction of the People (Numbers vi. 222 7), and on the Day of Atonement the High Priest pronounced it (Leviticus xvi. 30) amidst the prostrations of the assembled multitude. It is recorded in the Talmud that Rabbis communicated the true pronunciation to their disciples once in seven years (Qiddushin, 71a). The Jews called the tetragrammaton by a Hebrew denomination, Shem Hammephorash (שם ה..רש) i.e. the distinctive excellent name. It was considered an act of blasphemy for a layman to pronounce the tetragrammaton. This avoidance of the original name was due on the one hand to reverence and on the other to fear lest the name be desecrated by heathens. Partly in consequence of this mystery and partly in accord with widespread superstitions, the tetragrammaton figures in magical formulae from the time of the Gnostics, and on amulets. Many a medieval miracle-worker was supposed to derive his competence from his knowledge of the secret of the Name.
# 1911 Encyclopædia Britannica/Tetrazines

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​TETRAZINES, in organic chemistry, a group of compounds containing the ring system
C·N·N C·N·N C·N·C
Ċ·N·Ṅ, Ṅ·N·Ċ, Ṅ·N·Ṅ;
only derivatives of the first two types are known. The members of the first series may be prepared by oxidizing osazones (i.e. dihydrazones of α-diketones), dihydrotetrazines resulting. Dihydro-derivatives of the second type are formed from hydrazine and imino-ethers (A. Pinner, Ber., 1893, 26, p. 2126; 1894, 27, p. 984); these easily oxidize to the corresponding tetra zines, which are stable towards acids; their dihydro-derivatives, however, are decomposed, the group—NH-NH-being eliminated as hydrazine and replaced by oxygen, with consequent formation of the five membered oxybiazole ring. Concentrated acids convert the dihydro-tetra zines into isodihydrotetrazines, thus:—
R·C·NH·NH > R·C·NH·N
N̈·N :C̈·R N̈-NH-C-R,
the N-alkyl derivatives of which type may be prepared by the action of alcoholic potash and chloroform on aromatic hydrazines. I .
Much discussion has circulated about the decomposition of diazo-acetic ester, from which A. Hantzsch and O. Silberrad (Bern, 1900, 33, p. 58) obtained what they considered to be a dihydrotetrazine, thus:—
CH·CO$_2$R > HO$_2$C-CH-Nzlf g Hc-NH-151-IQ
N=N -CH-CO$_2$H N-NH-CH.
C. Bülow (Ber., 1906, 39, pp. 2618, 4106), however, showed this substance to be an N-aminotriazole, which necessitates the first decomposition product being an acid (I.), the conversion into the (I.) HO2C-(; ~NH~NH 9 (H) HOQC-ge-NZNH,
N-N: C-COQH ' N~N:C-CO2H
triazole derivative (II.) being due to the ring opening on the addition of the elements of water and then closing again to the five-membered ring with elimination of water again. The decompositions of diazoacetic ester were then again examined by T. Curtius and his students (Ber., 1907, 40, pp. 262, 350, 450, &c.), who showed that both triazole and tetra zine derivatives could be obtained from the Vbisdiazo-acetic acid which is formed by the action of alkali on diazo-acetic ester.
# 1911 Encyclopædia Britannica/Tester

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​TESTER (Fr, têtière, head-covering, from tête), anything placed horizontally over the head, as the sound-board of a pulpit, the fiat boards over an old-fashioned bed, &c.
# 1911 Encyclopædia Britannica/Tetradymite

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​TETRADYMITE, a mineral consisting of bismuth telluride and sulphite, Bi$_2$Te$_2$S, also known as "telluric bismuth." Sometimes sulphur is absent and the formula is then Bi$_2$Te$_3$; traces of selenium are usually present. Crystals are rhombohedral, but are rarely distinctly developed; they are twinned together in groups of four; hence the name of the mineral, from the Greek, τετραδῦμος, fourfold. There is a perfect cleavage parallel to the basal plane; and the mineral usually occurs in foliated masses of irregular outline. The colour is steel-grey, and the lustre metallic and brilliant. The mineral is very soft (H=11/2) and marks paper; the specific gravity is 7.2 to 7.6. It was first found, in 1815, at Telemarken in Norway; crystals are from Schubkau near Schemnitz in Hungary. It often occurs in quartz associated with native gold. Other species very similar to tetradymite, but with different formulae, are: joseite, from San José near Marianna in Brazil; grünlingite (Bi$_4$S$_3$Te), from Caldbeck Fells in Cumberland; and wehrlite, from Hungary.  (L. J. S.)
# 1911 Encyclopædia Britannica/Tetrahedron

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​TETRAHEDRON (Gr. τέτρα-, four, ἕδρα, face or base), in geometry, a solid bounded- by four triangular faces. It consequently has four vertices and six edges. If the faces be all equal equilateral triangles the solid is termed the “regular” tetrahedron. This is one of the Platonic solids, and is treated in the article Polyhedron, as is also the derived Archimedean solid named the “truncated tetrahedron”; in addition, the regular tetrahedron has important crystallographic relations, being the hemihedral form of the regular octahedron and consequently a form of the cubic system. The bisphenoids (the hemihedral forms of the tetragonal and rhombic bi pyramids), and the trigonal pyramid of the hexagonal system, are examples of non-regular tetrahedral (see Crystallography). “Tetrahedral co-ordinates” are a system of quadriplanar co-ordinates, fundamental planes being the faces of a tetrahedron, and co-ordinates the perpendicular distances of the point from faces, a positive sign being given if the point be between face and the opposite vertex, and a negative sign if not. If (u, v, w, t) be the co-ordinates of any point, then the relation u+v+w+t=R, where R is a constant, invariably holds. This system is of much service in following out mathematical, physical and chemical problems in which it is necessary to represent four variables.
Related to the tetrahedron are two spheres which have received much attention. The “twelve-point sphere,” discovered by P. M. E. Prouhet (1817–1867) in 1863, is somewhat analogous to the nine-point circle of a triangle. If the perpendiculars from the vertices to the opposite faces of a tetrahedron be concurrent, then a sphere passes through the four feet of the perpendiculars, and consequently through the centre of gravity of each of the four faces, and through the mid-points of the segments of the perpendiculars between the vertices and their common point of intersection. This theorem has been generalized for any tetrahedron; a sphere can be drawn through the four feet of the perpendiculars, and consequently through the mid-points of the lines from the vertices to the centre of the hyperboloid having these perpendiculars as generators, and through the orthogonal projections of these points on the opposite faces.
# 1911 Encyclopædia Britannica/Tetrarch

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​TETRARCH (τετράρχης), the ruler of a tetrarchy, that is, in the original sense of the word, of one quarter of a region. Such were the tetrarchies of Thessaly as reconstructed by Philip of Macedon and of Galatia before its conquest by the Romans (169 B.C.). In later times the title of tetrarch is familiar from the New Testament as borne by certain princes of the petty dynasties which the Romans allowed to exercise a dependent sovereignty within the province of Syria. In this application it has lost its original precise sense, and means only the ruler of part of a divided kingdom, or of a district too unimportant to justify a higher title. After the death of Herod the Great (4 B.C.) his realm was shared among his three sons: the chief part, including Judaea, Samaria and Idumaea, fell to Archelaus (Matt. ii. 22), with the title of ethnarch (Josephus, Antiq., xvii. 11, 4); Philip received the north-east of the realm and was called tetrarch; and Galilee was given to Herod Antipas, who bore the same title (Luke iii. 1). These three sovereign ties were reunited under Herod Agrippa from A.D. 41 to 44. In the same passage of Luke mention is made of Lysanias, tetrarch of Abilene near Damascus, in the valley of the Barada.
# 1911 Encyclopædia Britannica/Tetrastyle

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​TETRASTYLE (Gr. τέτρα-, four, and στῦλος, a column), the term in architecture given to a portico of four columns which forms the main front of a temple (q.v.).
# 1911 Encyclopædia Britannica/Somerville (New Jersey)

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​SOMERVILLE, a borough and the county-seat of Somerset county, New Jersey, U.S.A., in the north central part of the state, on the Raritan river, about 36 m. S.W. of New York City. Pop. (1890), 3861; (1900), 4843, of whom 560 were foreign-born; (1905), 4782; (1910), 5069. It is served by the Central Railroad of New Jersey and by inter-urban electric lines. Adjoining the borough on the west is the town of Raritan (pop. in 1910, 3672). Places of interest in Somerville are the Old Parsonage of the Dutch Reformed Church, built in 1750–1751 of brick imported from Holland by the Rev. Theodorus Jacobus Frelinghuysen, the first pastor; the Wallace House, built in 1778 and occupied by General Washington as his headquarters during the following winter, when the main army was in camp at Bound Brook; and Duke's Park (partly in Raritan), the immense private estate (laid out as a park and open to the public) of James B. Duke, president of the American Tobacco Company. Somerville has a fine county court house (1909) of Alabama white marble. Among the borough's manufactures are stoves, ranges, soil pipe, brick, woollen goods and shirts. Settlements were made within the present limits of Somerville in the last quarter of the 17th century, and the village was at first called Raritan, all that part of the Raritan Valley from Bound Brook to the junction of the north and south branches of the river, and including the present Somerville and Raritan, then being popularly called "Raritans." The present name was adopted in 1801. Somerville became the county-seat in 1783, after the destruction of the court-house in what is now the borough of Millstone (in Hillsborough township, about 6 m. south of Somerville) on the 27th of October 1779 by British troops under Colonel John Graves Simcoe ; it was incorporated as a town in 1863, and as a borough in 1909.
# 1911 Encyclopædia Britannica/Somersworth

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​SOMERSWORTH, a city of Strafford county, New Hampshire, U.S.A., on the Salmon Falls river, 5 m. N. of Dover, and opposite the town of Berwick, Maine, industrially a part of Somersworth. Pop. (1890) 6207; (1900) 7023 (3166 foreign-born); (1910) 6704. Somersworth is served by the Boston & Maine railroad, and is connected by electric line with Rochester and Dover. The river furnishes good water power, and the city’s chief interests are in the manufacture of cotton and woollen goods, and boots and shoes. It has a public library. In the south-west part is Central Park, lying along the shore of Willand’s Pond. The municipality owns and operates the waterworks. A settlement was established here in the latter part of the 17th century, when the territory was a part of Dover. In 1729 the parish of Summersworth was organized; in 1754 this parish was erected into the town of Somersworth; in 1821 the first company was formed to develop the water-power and establish cotton and woollen mills; in 1849 the southern half of the town was set-off and incorporated as Rollinsford; and in 1893 Somersworth was chartered as a city.
See W. D. Knapp, Somersworth, an Historical Sketch (1894).
# 1911 Encyclopædia Britannica/Somervile, William

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​SOMERVILE, WILLIAM (1675–1742), English poet, eldest son of a country gentleman, was born at Edstone, Worcestershire, on the 2nd of September 1675. He was educated at Winchester College and at New College, Oxford. After his father’s death in 1705 he lived on his estate, devoting himself especially to field sports, which supplied the subjects of his best-known poems. His publications were The Two Springs (1725), a fable; Occasional Poems. . . (1727) ; The Chase (1735) Hobbinol, or the Rural Games (1740), a burlesque poem; and Field Sports (1742), a poem on hawking. Somervile died on the 19th of July 1742.
His Chase passed through many editions. It was illustrated by Bewick (1796), by Stothard (1800), and by Hugh Thomson (1896), with a preface by R. F. Sharp.
# 1911 Encyclopædia Britannica/Sommer

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​SOMMER, in architecture, a girder or main beam of a floor; if supported on two storey posts and open below, it is called a bress or breast-summer. The word is also spelled “summer,” and is the same as “sumpter,” a pack-horse, Fr. sommier, O. Fr., saume, from Low Lat. salma, pack, burden, Gr. σάγμα, σάττειν, to fasten a pack on a horse.
# 1911 Encyclopædia Britannica/Somerville, Mary

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​SOMERVILLE, MARY (1780–1872), British scientific writer, was the daughter of Admiral Sir William George Fairfax, and was born on the 26th of December 1780 in the manse of Jedburgh, the house of her mother’s sister, wife of Dr Thomas Somerville (1741–1830), author of My Own Life and Times, whose son was her second husband. She received a rather desultory education, and mastered algebra and Euclid in secret after she had left school, and without any extraneous help. In 1804 she married her cousin, Captain Samuel Greig, who died in 1806; and in 1812 she married another cousin, Dr William Somerville (1771–1860), inspector of the army medical board, who encouraged and greatly aided her in the study of the physical sciences. After her marriage she made the acquaintance of the most eminent scientific men of the time, among whom her talents had attracted attention before she had acquired general fame, Laplace paying her the compliment of stating that she was the only woman who understood his works. Having been requested by Lord Brougham to translate for the Society for the Diffusion of Useful Knowledge the Mécanique Céleste of Laplace, she greatly popularized its form, and its publication in 1831, under the title of The Mechanism of the Heavens, at once made her famous. Her other works are the Connexion of the Physical Sciences (1834), Physical Geography (1848), and Molecular and Microscopic Science (1869). Much of the popularity of her writings was due to their clear and crisp style and the underlying enthusiasm for her subject which pervaded them. In 1835 she received a pension of £300 from government. She died at Naples on the 28th of November 1872. In the following year there appeared her Personal Recollections, consisting of reminiscences written during her old age, and of great interest both for what they reveal of her own character and life and the glimpses they afford of the literary and scientific society of bygone times.
# 1911 Encyclopædia Britannica/Sommerfeld

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​SOMMERFELD, a town of Germany, in the Prussian province of Brandenburg, on the Lubis, 40 m. S.E. of Frankfort-on-Oder, by the railway from Berlin to Breslau. Pop. (1905), 12,251. It has a Roman Catholic church, three Evangelical churches, several schools and a hospital. Its manufactures of woollen cloth are important; and it also contains finishing and dyeworks, an ironfoundry, boiler-works and breweries.
# 1922 Encyclopædia Britannica/Lankester, Sir Edwin Ray

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LANKESTER, SIR EDWIN RAY (1847-), English biologist, was born in London May 15 1847, eldest son of Edwin Lankester (1814-74), a well-known physician and naturalist and F.R.S. He was educated at St. Paul's school, Downing College, Cambridge, and Christ Church, Oxford. In 1870 he was made Radcliffe travelling fellow, and in 1872 was elected to a fellowship at Exeter College, Oxford. During 1874-90 he was professor of zoology and comparative anatomy at University College, London; from 1891 to 1898 he was Linacre professor of comparative anatomy at Oxford; and from 1898 to 1907 he was director of the natural history departments of the British Museum. He was created K.C.B. in 1907. He received hon. degrees from most of the universities of Europe and became a member of many
learned societies in England and America. His numerous publications include Comparative Longevity (1871); Degeneration (1880); and the more popular Science from an Easy Chair (1910); Diversions of a Naturalist (1915); Science and Education (1919) and Secrets of Earth and Sea (1920).
# 1922 Encyclopædia Britannica/Ladenburg, Albert

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LADENBURG, ALBERT (1842-1911), German chemist, was born at Mannheim July 2 1842. He was educated at a Realgymnasium at Mannheim and after the age of 15 at the technical school of Karlsruhe, proceeding to the university of Heidelberg, where he graduated as doctor of philosophy (1863). From 1863 to 1867 he first studied organic chemistry under A. Kekule at Ghent, then visited England, studied in Paris and with Ch. Friedel and Wurtz, and returned to teach at Heidelberg. In 1873 he went to Kiel as professor of chemistry and director of the laboratory, remaining there until 1889 when he went to the university of Breslau in the same capacity. He was made an honorary member of the Pharmaceutical Society of Great Britain in 1886 and received the Hanbury medal for original research in chemistry in 1889. Details of his work, especially in connexion with benzene derivatives, are given in 6.53, 55 and 942; 11.215; 20.430; 25.892 and 21.635. He published Entwicklungsgeschichte der Chemie von Lavoisier bis zur Gegenwart (1868) and other works on chemistry, collaborated in a Handwörterbuch der Chemie (13 vols., 1882-96), and wrote a volume of reminiscences, Lebenserinnerungen (1912). He died at Breslau Aug. 15 1911.
See Biographisches Jahrbuch und Deutscher Nekrolog., Bd. xvi., 171 (1914), and W. Herz's Albert Ladenburg.