and a lower Huronian group; the latter is subdivided into an
upper Animikean (north-east Minnesota) or Penokean (north-west
Wisconsin); a middle and a lower division. Each, of these four
groups is separated by marked unconformity from the rocks above
and below. Huronian rocks are well developed in the following
districts: the Marquette region of northern Michigan, comprising
quartzites, slates and conglomerates, with important iron-bearing
slates and schists and ferruginous cherts; in the Menominee district
of Michigan and Wisconsin similar rocks occur; the Penokee-Gogebic
district of Wisconsin and Michigan comprises quartzite's, shales and
limestones, with beds and dikes of diabase and olivine-gabbro;
the same rocks occur in the Crystal Falls, north Michigan; the Mesabi
and Vermilion districts, Minnesota, and north of Lake Michigan
rock groups of this age take an important place. The valuable iron
ores of Mesabi, Penokee-Gogebic and Menominee belong mainly to
the Animikean group; in the Penokee rocks of this age vast
thicknesses of igneous rocks constitute the greater part of the
formation. The Keweenawan rocks are said to attain the enormous
thickness of 50,000 ft.; the higher beds are mainly sandy sediments
and conglomerates; in the lower portions are great igneous masses,
gabbros, diabase and porphyries; thus in the St Croix valley, north-west
Wisconsin and Minnesota, no fewer than 65 lava flows and
conglomeratic beds have been counted, which together aggregate
some 20,000 ft. in thickness. Some of these lava flows appear to
have been due to fissure eruptions. The native copper deposits of
this age in north Michigan are the most extensive known.
Pre-Cambrian rocks occupy large areas and reach great thicknesses in the eastern provinces of Canada; in Newfoundland 10,000 ft. of strata lie between the Archean and Cambrian (the Terranovian series of South Hunt; Avalon group of others); similar rocks occur also north of the Great Lakes and in the Hudson Bay region. They are found also in great force in the Colorado Canyon, in the Adirondack Mountains, and Black Hills of S. Dakota and elsewhere.
Turning to Europe, we find pre-Cambrian rocks in Brittany, the “ phyllades de Saint Lô,” or Briovérian of Chas. Barrois; and along the western border of France and south-west of the central massif. In the Fichtelgebirge, the Silesian mountains and east Thuringia similar rocks occur; the Przibramer Schiefer of Lipold and rocks in J. Barrande's stage A are of this age. Probably the metamorphosed eruptive rocks on the southern border of the Hunsriick and Taunus are pre-Cambrian. Large tracts of metamorphic sedimentary rocks that may be classed here are found in Shantung and north China, and probably also in Brazil, India and Australia. In South Africa the gold-bearing Witwatersrand beds of the Transvaal and the overlying Ventersdorp and Potchefstroom systems; the Griqualand system and Cango and Ibeques systems of Cape Colony, all occur above Archean rocks and below those of Devonian age; they cannot as yet, therefore, be classed as pre-Cambrian and their age is still uncertain.
Little can be said of the climatic conditions of this remote period, the fossil evidence being so poor; but it is of interest to note that in certain regions, viz. in the Lake Huron region, in the Gaisa series of Varanger Fjord, Norway, and in the Yangtse district in China, conglomerate beds are found in which many of the boulders are scratched like those of the Dwyka beds of South Africa, and thus suggest the possibility of glacial conditions at some stages of the period.
For literature see Geological Literature added to the Geological Society's Library (annual). (J. A. H.)
PRECARIOUS, literally, held on the good-will of another, or on entreaty (Lat. prex, precis, prayer) to another. The word is used, in law, of a tenure of land, office, &c., held at the pleasure of another. In general usage it has the significance of something uncertain, dangerous or risky.
PRECEDENCE (from Lat. praecedere, to go before, precede). This word in the sense in which it is here employed means priority of place, or superiority of rank, in the conventional system of arrangement under which the more eminent and dignified orders of the community are classified on occasions of public ceremony and in the intercourse of private life. In the United Kingdom there is no complete and comprehensive code whereby the scheme of social gradation has been defined and settled, once and for all, on a sure and lasting foundation. The principles and rules at.present controlling it have been formulated at different periods and have been derived from various sources. The Crown is the fountain of honour, and it is its undoubted prerogative to confer on any of its subjects, in any part of its dominions, such titles and distinctions and such rank and place as to it may seem meet and convenient. Its discretion in this respect is altogether unbounded at common law, and is limited in those cases only wherein it» has been submitted to restraint by act of parliament. In the old time all questions of precedence came in the ordinary course of things within the jurisdiction of the court of chivalry, in which the lord high constable and earl marshal presided as judges, and of which the kings of arms, heralds and pursuivants were the assessors and executive officers. When, however, points of unusual moment and magnitude happened to be brought into controversy, they were occasionally considered and decided by the sovereign in person, or by a special commission, or by the privy council, or even by the parliament itself. But it was not until towards the middle of the 16th century that precedence was made the subject of any legislation in the proper meaning of the term.1 . In 1539 an act “ for the placing of the Lords in Parliament ” (31 Hen. VIII. c. Io) was passed at the instance of the king, and by it the relative rank of the members of the royal family, of the great olhcers of state and the household, and of the hierarchy and the peerage was definitely and definitively ascertained. In 1563 an act “for declaring the authority of the Lord Keeper of the Great Seal and the Lord Chancellor to be the same” (5 Eliz. c. 18) also declared their precedence to be the same. Questions concerning the precedence of peers are mentioned in the Lords Journals 4 & 5 Ph. and M. and 39 Eliz., but in the reign of James I. such questions were often referred to the commissioners for executing the office of earl marshal. In the reign of Charles I. the House of Lords considered several questions of precedence and objected in the earl of Banbury's case to warrants overruling the statute of 31 Hen. VIII. In 1689 an act “for enabling Lords Commissioners of the Great Seal to execute the office of Lord Chancellor or Lord Keeper ” (1 Will. and Mary c. 21) gave to the commissioners not being peers of the realm place next to the speaker of the House of Commons and to the speaker place next to the peers of the realm. In 1707 the Act of Union with Scotland (6 Anne c. 11) provided that all peers of Scotland should be peers of Great Britain? and should have rank immediately after the peers of the like degrees in England at the time of the union and before all peers of Great Britain of the like degrees created after the union. In 1800 the Act of Union with Ireland (39 & 40 Geo. III. c. 67) provided that the lords spiritual of Ireland should have rank immediately after the lords spiritual of the same degree in Great Britain, and that the lords temporal of Ireland should have rank immediately after the lords temporal of the same degree in Great Britain at the time of the union, and further that “ peerages of Ireland created after the union should have precedence with peerages of the United Kingdom created after the union according to the dates of their creation.” At different times too during the current century several statutes have been passed for the reform and extension of the judicial organization which have very materially affected the precedence of the judges, more especially the Tudicature Act of 1873 (36 & 37 Vict. c. 66), under which the lords justices of appeal and the justices of the High Court now receive their appointments. But the statute of Henry VIII. “ for the placing of the Lords ” still remains the only legislative measure in which it has been attempted to deal directly and systematically with any large and important section of the scale of general precedence; and the law, so far as it relates to the ranking of the sovereign's immediate kindred whether lineal or collateral, the principal ministers of the Crown and court, and both the spiritual and temporal members of the House of Lords, is to all practical intents and purposes what it was made by that statute nearly 350 years ago. Where no act of parliament applies precedence is determined either by the will and pleasure of the sovereign or by what is accepted as “ ancient usage and established
Ample materials for the satisfaction of the curiosity of those who are desirous of investigating the history of precedence under its wider and more remote aspects will be found in such writers as Selden or Mackenzie, together with the authorities quoted or referred to by them: Selden, Titles of Hono1', pt. ii. p. 740 seq. (London, 1672); Mackenzie, Observations upon The Laws and Customs of Nat-ions as to Preeedeney (Edinburgh, 1680; and also reprinted in Guillim, Display of Heraldry, 6th ed., London, 1724).
For the parliamentary rights of Scottish peers see article Peerage.
