includes north-west and south-west France, Spain, Italy, the Alps, the Fichtelgebirge, east Thuringia, Harz and Rhenish Mountains.
Authorities.—Sir R. I. Murchison, Silurian System (1839) and Siluria (1854, 1867); A. Sedgwick, Synopsis of the Classification 0} the British Palaeozoic Rocks (1855); J. Barrande, Systime siluriendu tentre de la Boheme (1852–1887); J. J. Bigsby, Thesaur-us Siluricus (London, 1868); J. E. Marr, The Classification of the Cambrian and Silurian Rocks (Cambridge, 1883); Charles Lapworth, "On the Geological Distribution of the Rhabdophora, " Annals and Mag. Nat. Hist. ser. 5, vols, iii., iv., v., vi. (1879–1880); B. N. Peach, J. Home, J. J. H. Teall, " The Silurian Rocks of Great Britain, " vol. i., Scotland, Mem. Geol. Survey (1899); F. Freeh and others, “Lethaea geognostica,” Theil i. Band 2 (Lethaea palaeozoica) (Stuttgart, 1897–1902); Sir A. Geikie, Text-book of Geology (4th ed., 1903); and for recent papers. Geological Literature, Geo!. Soc. (London, annual). See also Cambrian and Silurian Systems. (J. A. H.)
ORDU (anc. Cotyora, where the " Ten Thousand " embarked
for home), a town on the N. coast of Asia Minor, between Samsun
and Kerasund, connected with Zara, and so with Sivas, by a
carriage road, and with Constantinople and Trebizond by
steamer. Pop. about 6000, more than half Christian. Ordu has
exceptionally good Greek schools, and a growing trade in filberts.
ORDUIN-NASHCHOKIN, ATHANASY LAVRENTEVICH
(?–1680), Russian statesman, was the son of a poor official at
Pskov, who saw to it that his son was taught Latin, German and
mathematics. Athanasy began his public career in 1642 as one
of the delineators of the new Russo-Swedish frontier after the
peace of Stolbova. Even then he had a great reputation at
Moscow as one who thoroughly understood " German ways and
things." He was one of the first Muscovites who diligently
collected foreign books, and we hear of as many as sixty-nine
Latin works being sent to him at one time from abroad. He
attracted the attention of the young tsar Alexius by his resourcefulness
during the Pskov rebellion of 1650, which he succeeded in
localizing by personal influence. At the beginning of the
Swedish War, Orduin was appointed to a high command, in which
he displayed striking ability. In 1657 he was appointed minister-plenipotentiary
to treat with the Swedes on the Narova river.
He was the only Russian statesman of the day with sufficient foresight
to grasp the fact that the Baltic seaboard, or even a part
of it, was worth more to Muscovy than ten times the same
amount of territory in Lithuania, and, despite ignorant jealousy
of his colleagues, succeeded (Dec. 1658) in concluding a
three-years’ truce whereby the Muscovites were left in possession
of all their conquests in Livonia. In 1660 he was sent as plenipotentiary
to a second congress, to convert the truce of 1658
into a permanent peace. He advised that the truce with Sweden
should be prolonged and Charles II. of England invited to
mediate a northern peace. Finally he laid stress upon the
immense importance of Livonia for the development of Russian
trade. On being overruled he retired from the negotiations.
He was the chief plenipotentiary at the abortive congress of
Durovicha, which met in 1664, to terminate the Russo-Polish
War; and it was due in no small measure to his superior
ability and great tenacity of purpose that Russia succeeded in
concluding with Poland the advantageous truce of Andrussowo
(Feb. 11, 1667). On his return to Russia he was created
a boyar of the first class and entrusted with the direction
of the foreign office, with the title of " Guardian of the great
Tsarish Seal and Director of the great Imperial Offices." He
was, in fact, the first Russian chancellor. It was Orduin who
first abolished the onerous system of tolls on exports and imports,
and established a combination of native merchants for promoting
direct commercial relations between Sweden and Russia. He
also set on foot a postal system between Muscovy, Courland and
Poland, and introduced gazettes and bills of exchange into
Russia. With his name, too, is associated the building of the
first Russian merchant-vessels on the Dvina and Volga. But his
whole official career was a constant struggle with narrow routine
and personal jealousy on the part of the boyars and clerks of the
council. He was last employed in the negotiations for confirming
the truce of Andrussowo (September 1669; March 1670).
In January 1671 we hear of him as in attendance upon the tsar
on the occasion of his second marriage; but in February the
same year he was dismissed, and withdrew to the Kruipetsky
monastery near Kiev, where he took the tonsure under the name
of Antony, and occupied himself with good works till his death
in 1680. In many things he anticipated Peter the Great. He
was absolutely incorruptible, thus standing, morally as well as
intellectually, far above the level of his age.
See S. M. Solovev, History of Russia (Rus.), vol. xi. (St Petersburg, 1895, seq.); V. Ikonnikov, " Biography of Orduin-Nashchokin " (in Russkaya Starina, Nos. 11-12) (St Petersburg, 1883); R. Nisbet Bain, The First Romanovs (London, 1905, chaps. 4 and 6). (R. N. B.)
ÖREBRO, a town of Sweden, capital of the district län) of
Örebro, lying on both banks of the Svartå a mile above its entrance
into Lake Hjelmar, 135 m. W. of Stockholm by rail. Pop. (1900),
22,013. In great part rebuilt since a fire in 1854, it has a modern
appearance. An ancient castle, however, with four round towers,
remains on an island in the stream. It is used as a museum.
There may be mentioned also the church of St Nicholas, of the
13th century; and the King's House (Kungsstuga), an old and
picturesque timber building. In front of the modern town hall
stands a statue, by Karl Gustav Qvarnström (1810–1867), of the
patriot Engelbrecht (d. 1436), who was born here. The Swedish
reformers of the 16th century, Olaus and Laurentius Petri, are
commemorated by an obelisk. Örebro is in closing connexion with
the iron-mining district of central Sweden; it has mechanical
works and a technical college. A large trade is carried on, by
way of the Orebro canal and lakes Hjelmar and Mälar, with
Stockholm.
Örebro was in existence in the 11th century. Its castle, erected by Birger Jarl in the 13th century, played an important part in the early annals of Sweden; and no fewer than twenty diets or important assemblies were held either in the castle or in the town. Such were the Örebro concilium of 1537, the diet of 1540 in which the crown was declared hereditary, and that of 1810 when Bernadotte was elected crown prince.
ORE-DRESSING, one of the principal processes in the work of mining (q.v.). When the miner hoists his ore[1] to the surface, the
contained metal may be either in the native uncombined state,
as, for example, native gold, native silver, native copper,
or combined with other substances forming minerals of more
or less complex composition, as, for example, telluride of gold,
sulphide of silver, sulphide of copper. In both cases the
valuable mineral is always associated with minerals of no value.
The province of the ore-dresser is to separate the " values "
from the waste—for example, quartz, felspar, calcite—by mechanical
means, obtaining thereby "concentrates" and "tailings."
The province of the metallurgist is to extract the pure metal
from the concentrates by chemical means, with or without the
aid of heat. There are also a number of non-metallic minerals
which do not have any value, or at best do not reach their highest
value until they have been subjected to some form of mechanical
preparation; among them are diamonds, graphite, corundum,
garnet, asbestos and coal. Ore-dressing, for the purposes of this
article, may be divided into three parts: (1) properties of
minerals which render aid in their separation; (2) simple operations;
(3) operations combined to form processes or mills.
I. The specific gravity of minerals varies greatly, some being heavy, others light. The rate of settling in water is affected by the specific gravity in this way: of two particles of the same /vonert/es size but different specific gravity, the heavier settles more rapidly than the lighter, while of two particles of different specific gravity which settle at the same rate in water, that of higher specific gravity is of smaller diameter than the other. The same statements are true in regard to settling in air, and in regard to momentum in air when the particles are thrown out in a horizontal direction. Colour, lustre and fracture are of especial value in hand-picking, to aid the eye in selecting the mineral sought. Instances are, of colours, the white of quartz, the pale straw colour of felspar, the dull yellow of limonite, the brass yellow of chalcopyrite, the pale metallic yellow of pyrite; of lustres, the vitreous of quartz, the adamantine of diamond and cerussite, the resinous of blende, the earthy of limonite, and the metallic of pyrite; and of fractures, the cleavage planes of felspar and galena, the conchoidal fracture of quartz and pyrite, the granular of some forms of magnetite and blende. Magnetism is a most direct and simple method of separating minerals where it is available. The discovery that by the use of electro-magnets of great
- ↑ The O. Eng. word was ōra, corresponding with Du. oer, the origin of which is unknown. The form " ore " represents the O.Eng. ār, brass; cf. Lat. aes, Skt. ayas.
