Chapter III: General Observations (3)

_Geology._--Almost the entire area of this county is occupied by the
younger Highland schists and metamorphic rocks. East of Loch Ericht
and the rivers Traim and Spey as far as Airemore and between there and
Duthel there are quartzites and quartzose schists; on the remaining
area the various kinds of schistose and gneissose rock have hardly
been worked out in detail. Granite masses occur in numerous isolated
patches; the largest is on the eastern boundary and includes the
flanks of Cairn Gorm, Cairn Tout, Braeriach, Carn Ban and Meall
Tisnail. Other smaller ones are found at Ben Nevis, where the lower
part of the mountain is granite, the upper part porphyritic felsite;
between Moy and Ben Buidhe Mhor; E. of Foyers, including Whitebridge,
Aberchalder and Loch Farraline; at Ben Alder, W. of Loch Ericht and
another between that loch and the river Pattack; at Banavie on the W.
of the river Lochy; around the upper end of Loch Clunie and at several
other places. The dioritic mass of Rannoch Moor just enters this
county between Loch Ericht and Loch Ossian.

The Old Red Sandstone extends into this county from Nairn through
Culloden Moor past Inverness and down Loch Ness to a point south of
Foyers; it occurs also on the south-east side of Loch Oich, and around
Beauly, where it forms the falls of Kilmorach. These rocks consist at
the base of coarse breccias and conglomerates passing upwards into
chocolate-coloured sandstone and flags, with the shaly series
containing limestone nodules known as the fish bed from the abundance
and importance of its fossil contents; it is well exposed in the Big
Burn and near Loch Ashie. At a higher horizon come more purple flags
and grits. The Great Glen which traverses the county is an old line of
earth fracture along which displacements have been produced during
more than one geological period. Roches moutonnees, glacial striations
and moraines and other evidences of the great Ice age are abundant,
besides the parallel roads of Glen Roy to which allusion has already
been made. The lowest of these terraces is prolonged into Glen Spean.
At numerous places on the coasts the remains of old marine terraces
occur at 100 ft. and 25 ft. above the sea.

Of the small isles belonging to Inverness-shire those of Rum and Eigg
are of the greatest interest. The northern part of Rum is made of
Torridonian rocks, shales below and red sandstones above; altogether
over 10,000 ft. are visible. These rocks have suffered thrusting and
the shales are thus made in places to overlie the sandstones. A few
patches of Torridonian occur in the south. Tertiary peridotites in
laccolitic masses cover a large area in the south of the island and
form the highest ground. These are penetrated by eucrites and gabbros,
followed later by granites; and the whole has been subsequently
crushed into a complex gneissose mass. Still later, dolerite sills and
sheets and dikes of granophyre and quartz felsite followed in the same
region. Eigg is mainly built of great basaltic lava flows with
intrusions of doleritic rocks; these were succeeded by more acid
intrusions, and again by a more basic series of dikes. Pitchstones
occur among the later rocks. The Sgurr is capped by a thick intrusion
of pitchstone. Jurassic rocks, including the Estuarine Lower Oolite
sandstones, shales and limestones and Middle Oolite Oxfordian rocks
are found in the north of this island; there is also a small trace of
Upper Cretaceous sandstone. Canna, Sanday and Muck are almost wholly
basaltic; a small patch of Jurassic occurs on the south of the
last-named island. (See also SKYE.)

_Forests and Fauna._--Deer forests occupy an enormous area, particularly in the west, in the centre, in the south and south-east and in Skye. From the number of trees found in peat bogs, the county must once have been thickly covered with wood. Strathspey is still celebrated for its forests, and the natural woods on Loch Arkaig, in Glen Garry, Glen Moriston, Strathglass and Strathfarrar, and at the head of Loch Sheil, are extensive. The forests consist chiefly of oak, Scotch fir, birch, ash, mountain-ash (rowan), holly, elm, hazel and Scots poplar, but there are also great plantations of larch, spruce, silver fir, beech and plane. Part of the ancient Caledonian forest extends for several miles near the Perthshire boundary. Red and roe deer, the Alpine and common hare, black game and ptarmigan, grouse and pheasant abound on the moors and woodlands. Foxes and wild cats occur, and otters are met with in the lakes and streams. There are also eagles, hawks and owls, while great flocks of waterfowl, particularly swans, resort to Loch Inch and other lakes in Badenoch. Many of the rivers and several of the lochs abound with salmon and trout, the salmon fisheries of the Beauly, Ness and Lochy yielding a substantial return.

_Climate and Agriculture._--Rain is heavy and frequent in the mountains, but slighter towards the northern coast; the fall for the year varying from 73.17 in. at Fort William to 43.17 in. at Fort Augustus, and 26.53 in. at Inverness. The mean temperature for the year is 47.2 deg. F., for January 38.5 deg. and for August 58 deg. Although since 1852 the cultivated area has increased greatly, actually the percentage of land under crops is still small. The Aird and Beauly districts, some of the straths and several of the glens are fertile. Oats are the predominant crop, barley is grown (mostly for the distilleries), but the wheat acreage is trifling. Of green crops turnips do well in certain districts, artificial manures being extensively used. In those quarters where the soil is dry, potatoes are successfully raised. An immense number of the holdings are crofts averaging 5 acres or under. About 50% are between 5 acres and 50; but few are above 50. The operations of the Crofters' Commission (1886) have been beneficial in a variety of ways. Not only have rentals been reduced considerably and arrears cancelled, but the increased sense of security resulting from the granting of fair rentals, fixity of tenure and compensation for disturbance has induced tenants to reclaim waste land, to enlarge their holdings and to apply themselves more thriftily and with greater enterprise and intelligence to the development of their farms. On the large holdings the most modern methods of husbandry are followed, the farm buildings are excellent and the implements up-to-date. The hills furnish good pastures. The flocks of sheep are exceptionally heavy, the chief varieties on the uplands being Cheviots and black-faced and in some of the lower districts Leicesters and half-breeds. Of the cattle the principal breed is the Highland, the largest and best herds of which are in the Western Isles. Polled and shorthorns are also reared, and Ayrshires are kept for dairy purposes. Great numbers of the hardy Highland ponies are raised on the hill farms, and the breed of agricultural horses was improved by the introduction of Clydesdale stallions. Where pigs are reared they appear to be kept, especially amongst the crofters, for domestic consumption.

_Industries._--Manufactures are few. Indeed, excepting the industries carried on in Inverness, they are almost entirely confined to distilling--at Fort William, Kingussie, Carbost, Muir of Ord and some other places--brewing, woollens (especially tartans, plaids and rough tweeds), milling and (at Kirktown near Inverness) artificial manures. The catering for the wants of thousands of sportsmen and tourists, however, provides employment for a large number of persons, and has led to the opening of hotels even in the remotest regions. The fisheries, on the other hand, are of great value, especially to the Hebrideans. The kelp industry has died out.

_Communications._--Owing to its physical character communication by rail is somewhat restricted, but the Highland railway enters the shire from the south near Dalwhinnie and runs to Inverness via Aviemore and Daviot. Another portion of the same system also reaches the county town from Nairnshire. The Dingwall and Skye railway passes along the southern shore of Beauly Firth. In the south-west the West Highland railway (North British) enters the county 2 m. N.W. of Rannoch station and terminates at Mallaig, via Fort William and Banavie, sending off at Spean Bridge a branch to Fort Augustus. There is also communication by steamer with the piers of the Caledonian Canal and with the Western Isles, and a considerable amount of shipping reaches Beauly and Inverness by way of Moray Firth. Coaches supplement rail and steamer at various points.

_Population and Government._--The population was 90,121 in 1891, and 90,104 in 1901, when 43,281 persons spoke Gaelic and English, and 11,722 Gaelic only. The only considerable towns are Inverness (pop. in 1901, 23,066) and Fort William (2087). The county returns one member to parliament, but the county town, along with Forres, Fortrose and Nairn, belongs to the Inverness district group of parliamentary burghs. Inverness forms a sheriffdom with Elgin and Nairn, and there are resident sheriffs-substitute at Inverness, Fort William, Portree and Lochmaddy. The county is under school-board jurisdiction, and there are voluntary schools (mostly Roman Catholic) in several places. The secondary schools in Inverness and some in the county earn grants for higher education. The town council of Inverness subsidizes the burgh technical and art school. At Fort Augustus is a well-known collegiate institution for the education of the sons of well-to-do Roman Catholics.

_History._--To the north of the boundary hills of the present counties of Argyll and Perth (beyond which the Romans attempted no occupation) the country was occupied by the Picts, the true Caledonians. The territory was afterwards called the province of Moray, and extended from the Spey and Loch Lochy to Caithness. These limits it retained until the 17th century, when Caithness (in 1617), Sutherland (in 1633) and Ross-shire (in 1661) were successively detached. Towards the end of the 6th century Columba undertook the conversion of the Picts, himself baptizing their king, Brude, at Inverness; but paganism died hard and tribal wars prevented progress. In the 11th century, after the death of Duncan, Scotland was divided between Macbeth and the Norwegian leader Thorfinn, who took for his share the land peopled by the northern Picts. Malcolm Canmore, avenging his father, defeated and slew Macbeth (1057), and at a later date reduced the country and annexed it to the kingdom of Scotland. In 1107, when the bishopric of Moray was founded, the influence of the Church was beginning to effect some improvement in manners. Nevertheless, a condition of insurrection supervened until the reign of David I., when colonists of noble birth were settled in various parts of the shire. After the battle of Largs (1263) the Norse yoke was thrown off. In 1303 Edward I.'s expedition to Scotland passed through the northern districts, his army laying siege to Urquhart and Beaufort castles. After the plantation the clan system gradually developed and attained in the shire its fullest power and splendour. The Frasers occupied the Aird and the district around Beauly; the Chisholms the Urquhart country; the Grants the Spey; the Camerons the land to the west and south of Loch Lochy (Locheil); the Chattan--comprising several septs such as the Macphersons, Mackintoshes, Farquharsons and Davidsons--Badenoch; the Macdonalds of the Isles Lochaber; the Clanranald Macdonalds Moidart, Knoydart, Morar, Arisaig and Glengarry; and the Macleods Skye. Unfortunately the proud and fiery chieftains were seldom quiet. The clans were constantly fighting each other, occasionally varying their warfare by rebellion against the sovereign. In many quarters the Protestant movement made no headway, the clansmen remaining steadfast to the older creed. At the era of the Covenant, Montrose conducted a vigorous campaign in the interests of the Royalists, gaining a brilliant victory at Inverlochy (1645), but the effects of his crusade were speedily neutralized by the equally masterly strategy of Cromwell. Next Episcopacy appeared to be securing a foothold, until Viscount Dundee fell at Killiecrankie, that battle being followed by a defeat of the Highlanders at Cromdale in 1690. The futile rising headed by Mar in 1715 led to a combined effort to hold the clans in check. Forts were constructed at Inverness, Kilchumin (Fort Augustus) and Kilmallie (Fort William); Wade's famous roads--exhibiting at many points notable examples of engineering--enabled the king's soldiers rapidly to scour the country, and general disarming was required. Prince Charles Edward's attempt in 1745 had the effect of bringing most of the clans together for a while; but the clan system was broken up after his failure and escape. Heritable jurisdictions were abolished. Even the wearing of the Highland dress was proscribed. The effects of this policy were soon evident. Many of the chieftains became embarrassed, their estates were sold, and the glensfolk, impoverished but high-spirited, sought homes in Canada and the United States. As time passed and passion abated, the proposal was made to raise several Highland regiments for the British army. It was entertained with surprising favour, and among the regiments then enrolled were the 79th Cameron Highlanders. With the closing of the chapter of the Jacobite romance the shire gradually settled down to peaceful pursuits.

The county in parts is rich in antiquarian remains. Stone axes and other weapons or tools have been dug up in the peat, and prehistoric jewelry has also been found. Lake dwellings occur in Loch Lundy in Glengarry and on Loch Beauly, and stone circles are numerous, as at Inches, Clava, and in the valley of the Ness. Pictish towers or brochs are met with in Glenbeg (Glenelg), and duns (forts) in the Aird and to the west and south-west of Beauly and elsewhere. Among vitrified forts the principal are those on Craig Phadrick, Dundbhairdghall in Glen Nevis, Dun Fionn or Fingal's fort on the Beauly, near Kilmorack, Achterawe in Glengarry and in Arisaig.

See J. Cameron Lees, _History of the County of Inverness_ (Edinburgh,
1897); C. Fraser-Mackintosh, _Letters of Two Centuries_ (Inverness,
1890); Alexander Mackenzie, _Histories of the Mackenzies_, Camerons,
&c. (Inverness, 1874-1896); A. Stewart, _Nether Lochaber_ (Edinburgh,
1883); Alexander Carmichael, "Grazing and Agrestic Customs of the
Outer Hebrides" (_Crofters' Commission Report_, 1884).

INVERSION (Lat. _invertere_, to turn about), in chemistry, the name given to the hydrolysis of cane sugar into a mixture of glucose and fructose (invert sugar); it was chosen because the operation was attended by a change from dextro-rotation of polarized light to a laevo-rotation. In mathematics, inversion is a geometrical method, discovered jointly by Stubbs and Ingram of Dublin, and employed subsequently with conspicuous success by Lord Kelvin in his electrical researches. The notion may be explained thus: If R be a circle of centre O and radius r, and P, Q be two points on a radius such that OP.OQ = r^2, then P, Q are said to be inverse points for a circle of radius r, and O is the centre of inversion. If one point, say P, traces a curve, the corresponding locus of Q is said to be the inverse of the path of P. The fundamental propositions are: (1) the inverse of a circle is a line or a circle according as the centre of inversion is on or off the circumference; (2) the angle at the intersection of two circles or of a line and a circle is unaltered by inversion. The method obviously affords a ready means for converting theorems involving lines and circles into other propositions involving the same, but differently placed, figures; in mathematical physics it is of special value in solving geometrically electrostatical and optical problems.

INVERURIE, a royal, municipal and police burgh of Aberdeenshire, Scotland, situated at the confluence of the rivers Don and Ury, 16(1/4) m. N.W. of Aberdeen by rail, on the Great North of Scotland railway. Pop. (1901) 3624. Paper-making, milling, and the making of mineral waters are the chief manufactures, but the town is an important centre of the cattle trade with London, markets being held at frequent intervals. It also contains the workshops of the Great North of Scotland railway. Inverurie belongs to the Elgin district group of parliamentary burghs. At Harlaw, about 3 m. to the N.W., was fought in 1411 the great battle between Donald, lord of the Isles, and the royal forces under the earl of Mar. Not far from the scene of this conflict stands Balquhain Castle, a seat of the Leslies, now a mere shell, which was occupied by Queen Mary in September 1562 before the fight at Corrichie between her forces, led by the earl of Moray, and those of the earl of Huntly. The granite block from which she is said to have viewed the combat is still called the Queen's Chair or the Maiden Stone. Near Bennachie (1619 ft.) are stone circles and monoliths supposed to be of Druidical origin. There is a branch line from Inverurie to Old Meldrum, 5(3/4) m. to the N.E. by rail, a market town with a charter dating from 1672, where brewing and distilling are carried on.

INVESTITURE (Late Lat. _investitura_), the formal installation into an office or estate, which constituted in the middle ages one of the acts that betokened the feudal relation between suzerain and vassal. The suzerain, after receiving the vassal's homage and oath of fealty, invested him with his land or office by presenting some symbol, such as a clod, a banner, a branch, or some other object according to the custom of the fief. Otto of Freising says: "It is customary when a kingdom is delivered over to any one that a sword be given to represent it, and when a province is transferred a standard is given." As feudal customs grew more stereotyped, the sword and sceptre, emblematic respectively of service and military command and of judicial prerogatives, became the usual emblems of investiture of laymen. The word investiture (from _vestire_, to put in possession) is later than the 9th century; the thing itself was an outcome of feudal society.

It is in connexion with the Church that investiture has its greatest historical interest. The Church quite naturally shared in feudal land-holding; in addition to the tithes she possessed immense estates which had been given her by the faithful from early times, and for the defence of which she resorted to secular means. The bishops and abbots, by confiding their domains to laymen on condition of assistance with the sword in case of need, became temporal lords and suzerains with vassals to fight for them, with courts of justice, and in short with all the rights and privileges exercised by lay lords. On the other hand there were bishop-dukes, bishop-counts, &c., themselves vassals of other lords, and especially of the king, from whom they received the investiture of their temporalities. Many of the faithful founded abbeys and churches on condition that the right of patronage, that is the choice of beneficiaries, should be reserved to them and their heirs. Thus in various ways ecclesiastical benefices were gradually transformed into fiefs, and lay suzerains claimed the same rights over ecclesiastics as over other vassals from whom they received homage, and whom they invested with lands. This ecclesiastical investiture by lay princes dates at least from the time of Charlemagne. It did not seem fitting at first to confer ecclesiastical investiture by such military and worldly emblems as the sword and sceptre, nor to exact an oath of fealty. The emperor Henry I. invested bishops with a glove; Otto II. presented the pastoral staff; Conrad II., according to Wipo, went farther and required from the archbishop of Milan an oath of fealty. By the time of Henry III. investiture with ring and crozier had become the general practice: it probably had been customary in some places since Otto II.

Investiture of ecclesiastics by laymen had certain serious effects which were bound to bring on a conflict between the temporal and spiritual authorities. In the first place the lay authorities often rendered elections uncanonical by interfering in behalf of some favourite, thereby impairing the freedom of the electors. Again, benefices were kept vacant for long periods in order to ensure to the lord as long as possible the exercise of his regalian rights. And, finally, control by temporal princes of investiture, and indirectly of election, greatly increased simony. Otto II. is charged with having practised simony in this connexion, and under Conrad II. the abuse grew prevalent. At a synod at Reims in 1049, the bishops of Nevers and Coutances affirmed that they had bought their bishoprics, and the bishop of Nantes stated that his father had been a bishop and that on his decease he himself had purchased the see. At a synod at Toulouse in 1056, Berengar of Narbonne accused the bishop of having purchased his see for 100,000 _solidi_, and of having plundered his church and sold relics and crucifixes to Spanish Jews in order to secure another 100,000 _solidi_ with which to buy for his brother the bishopric of Urgel. Innumerable similar cases appear in acts of synods and in chronicles during the 11th century. Ecclesiastical investiture was further complicated by the considerable practice of concubinage. There was always the tendency for clerics in such cases to invest their sons with the temporalities of the Church; and the synod convened by Benedict VIII. at Pavia in 1018 (or 1022 according to some authorities) was mainly concerned with the issue of decrees against clerics who lived with wives or concubines and bestowed Church goods on their children. In time the Church came to perceive how closely lay investiture was bound up with simony. The sixth decree of the Lateran synod of 1059 forbade any cleric to accept Church office from a layman. In the following year this decree was reaffirmed by synods held at Vienne and Toulouse under the presidency of a legate of Nicholas II. The main investiture struggle with the empire did not take place, however, until Hildebrand became Pope Gregory VII. To Gregory it was intolerable that a layman, whether emperor, king or baron, should invest a churchman with the emblems of spiritual office; ecclesiastical investiture should come only from ecclesiastics. To the emperor Henry IV. it was highly undesirable that the advantages and revenues accruing from lay investiture should be surrendered; it was reasonable that ecclesiastics should receive investiture of temporalities from their temporal protectors and suzerains.

Although the full text of the decrees of the famous Lenten synod of 1075 has not been preserved, it is known that Gregory on that occasion denounced the marriage of the clergy, excommunicated five of Henry IV.'s councillors on the ground that they had gained church offices through simony, and forbade the emperor and all laymen to grant investiture of bishopric or inferior dignity. The pope immediately summoned Henry to appear at Rome in order to justify his private misconduct, and Henry replied by causing the partisan synod of Worms (1076) to pronounce Gregory's deposition. The pope excommunicated the emperor and stirred up civil war against him in Saxony with such success that he brought about Henry's bitter humiliation at Canossa in the following year. The papal prohibition of lay investiture was renewed at synods in 1078 and 1080, and although Gregory's death in exile (1085) prevented him from realizing his aim in the matter, his policy was steadfastly maintained by his successors. Victor III. condemned lay investiture at the synod of Benevento in 1087, and Urban II. at that of Melfi in 1089. At the celebrated council of Clermont (1095), at which the first crusade was preached, Urban strengthened the former prohibitions by declaring that no one might accept any spiritual office from a layman, or take an oath of fealty to any layman. Urban's immediate successor, Paschal II., stirred up the rebellion of the emperor's son, but soon found Henry V. even more persistent in the claim of investiture than Henry IV. had been. Several attempts at settlement failed. In February 1111 legates of Paschal II. met Henry V. at Sutri and declared that the pope was ready to surrender all the temporalities that had been bestowed on the clergy since the days of Charlemagne in return for freedom of election and the abolition of lay investiture. Henry, having agreed to the proposal, entered Rome to receive his crown. The bishops and clergy who were present at the coronation protested against this surrender, and a tumult arising, the ceremony had to be abandoned. The king then seized pope and curia and left the city. After two months of close confinement Paschal consented to an unqualified renunciation on his part of the right of investiture. In the following year, however, a Lateran council repudiated this compact as due to violence, and a synod held at Vienne with papal approval declared lay investiture to be heresy and placed Henry under the ban. The struggle was complicated throughout its course by political and other considerations; there were repeated rebellions of German nobles, constant strife between rival imperial and papal factions in the Lombard cities and at Rome, and creation of several anti-popes, of whom Guibert of Ravenna (Clement III.) and Gregory VIII. were the most important. Final settlement of the struggle was retarded, moreover, by the question of the succession to the lands of the great Countess Matilda, who had bequeathed all her property to the Holy See, Henry claiming the estates as suzerain of the fiefs and as heir of the allodial lands. The efforts of Gelasius II. to settle the strife by a general council were rendered fruitless by his death (1119).

At length in 1122 the struggle was brought to an end by the concordat of Worms, the provisions of which were incorporated in the eighth and ninth canons of the general Lateran council of 1123. The settlement was a compromise. The emperor, on the one hand, preserved feudal suzerainty over ecclesiastical benefices; but, on the other, he ceased to confer ring and crozier, and thereby not only lost the right of refusing the elect on the grounds of unworthiness, but also was deprived of an efficacious means of maintaining vacancies in ecclesiastical offices. Few efforts were made to undo the compromise. King Lothair the Saxon demanded of Innocent II. the renewal of lay investiture as reward for driving the antipope Anacletus from Rome, but the opposition of St Bernard and the German prelates was so potent that the king dropped his demand, and Innocent in 1133 confirmed the concordat. In fact, the imperial control over the election of bishops in Germany came later to be much curtailed in practice, partly by the tacitly changed relations between the empire and its feudatories, partly by explicit concessions wrung at various times from individual emperors, such as Otto IV. in 1209 and Frederick II. in 1213; but the principles of the concordat of Worms continued theoretically to regulate the tenure of bishoprics and abbacies until the dissolution of the empire on 1806.

In France the course of the struggle was somewhat different. As in the empire, the king and the nobles, each within his own sphere of influence, claimed the right of investing with ring and crozier and of exacting homage and oaths of fealty. The struggle, however, was less bitter chiefly because France was not a united country, and it was eventually terminated without formal treaty. The king voluntarily abandoned lay investiture and the claim to homage during the pontificate of Paschal II., but continued to interfere with elections, to appropriate the revenues of vacant benefices, and to exact an oath of fealty before admitting the elect to the enjoyment of his temporalities. Most of the great feudal lords followed the king's example, but their concessions varied considerably, and in the south of France some of the bishops were still doing homage for their sees until the closing years of the 13th century; but long before then the right of investing with ring and crozier had disappeared from every part of France.

England was the scene of an investiture contest in which the chief actors were Henry I. and Anselm. The archbishop, in obedience to the decrees of Gregory VII. and Urban II., not only refused to perform homage to the king (1100), but also refused to consecrate newly-chosen bishops who had received investiture from Henry. The dispute was bitter, but was carried on without any of the violence which characterized the conflict between papacy and empire; and it ended in a compromise which closely foreshadowed the provisions of the concordat of Worms and received the confirmation of Paschal II. in 1106. Freedom of election, somewhat similar in form to that which still exists, was formally conceded under Stephen, and confirmed by John in Magna Carta.

Many documents relating to the investiture struggle have been edited
by E. Dummler in _Monumenta Germaniae historica, Libelli de lite
imperatorum et pontificum saeculis xi. et xii._ (3 vols., 1891-1897),
See Ducange, _Glossarium_, s.v. "Investitura."

On investiture in the empire consult C. Mirbt, _Die Publizistik im
Zeitalter Gregors VII._ (Leipzig, 1894); E. Bernheim, _Das Wormser
Konkordat_ (Breslau, 1906); R. Boerger, _Die Belehnungen der deutschen
geistlichen Fursten_ (Leipzig, 1901); K. E. Benz, _Die Stellung der
Bischofe von Meissen, Merseburg und Naumburg im Investiturstreite
unter Heinrich IV. und Heinrich V._ (Dresden, 1899); W. Martens,
_Gregor VII., sein Leben und Wirken_ (2 vols., Leipzig, 1894); P.
Fisher, _The Medieval Empire_, c. 10 (London, 1898). For France, see
P. Imbart de la Tour, _Les Elections episcopales dans l'eglise de
France du XI^e au XII^e siecle_ (Paris, 1891); A. Luchaire,
_Histoire des institutions monarchiques de la France sous les premiers
Capetiens 987-1180_ (2nd ed., Paris, 1891); P. Viollet, _Histoire des
institutions politiques et administratives de la France_ (Paris,
1898); Ibach, _Der Kampf zwischen Papsttum und Konigtum von Gregor
VII. bis Calixto II._ (Frankfort, 1884). For England, see J. F.
Bohmer, _Kirche und Staat in England und in der Normandie in XI. und
XII. Jahrhundert_ (Leipzig, 1899); E. A. Freeman, _The Reign of
William II. Rufus and the Accession of Henry I._ (London, 1882); H. W.
C. Davis, _England under the Normans and Angevins_ (London, 1905).

INVOICE (originally a plural, _Invoyes_ or _Invoys_, of _Invoy_, a variant of "envoy," from the French _envoyer_, to send), a statement giving full particulars of goods sent or shipped by a trader to a customer, with the quantity, quality and prices, and the charges upon them. Consular invoices, i.e. invoices signed at the port of shipment by a consul of the country to which the goods are being consigned, are generally demanded by those countries which impose _ad valorem_ duties.

INVOLUTION (Lat. _involvere_, to roll up), a rolling up or complication. In arithmetic, involution is the operation of raising a quantity to any power; it is the converse of evolution, which is the operation of extracting any root of a quantity (see ARITHMETIC; ALGEBRA). In geometry, an involution is a one-to-one correspondence between two ranges of points or between two pencils (see GEOMETRY: _Projective_). The "involute" of a curve may be regarded as the locus of the extremity of a string when it is unwrapped from the curve (see INFINITESIMAL CALCULUS).

IO, in Greek mythology, daughter of Inachus, the river-god of Argos and its first king. As associated with the oldest worship of Hera she is called the daughter of Peiren, who made the first image of that goddess out of a pear-tree at Tiryns; and under the name of Callithyia Io was regarded as the first priestess of Hera. Zeus fell in love with her, and, to protect her from the wrath of Hera, changed her into a white heifer (Apollodorus ii. 1; Hyginus, _Fab._ 145; Ovid, _Metam._ i. 568-733); according to Aeschylus (_Supplices_, 299) the metamorphosis was the work of Hera herself. Hera, having persuaded Zeus to give her the heifer, set Argus Panoptes to watch her. Zeus thereupon sent Hermes, who lulled Argus to sleep and cut off his head with the sword with which Perseus afterwards slew the Gorgon. In another account Argus is killed by a stone thrown by Hermes. But the wrath of Hera still pursued Io. Maddened by a gadfly sent by the goddess she wandered all over the earth, swam the strait known on this account as the Bosporus (Ox-ford), and crossed the Ionian sea (traditionally called after her) until at last she reached Egypt, where she was restored to her original form and became the mother of Epaphus. Accounts of her wanderings (differing considerably in detail) are given in the _Supplices_ and _Prometheus Vinctus_ of Aeschylus. Various interpretations are given of the latter part of her story, which dates from the 7th century B.C., when intercourse was frequent between Greece and Egypt, and when much influence was exerted on Greek thought by Egyptian religion. According to the rationalistic explanation of Herodotus (i. 1) Io was an Argive princess who was carried off to Egypt by the Phoenicians. Epaphus, the son of Io, the supposed founder of Memphis, was identified with Apis. He was said to have been carried off by order of Hera to Byblus in Syria, where he was found again by Io. On returning to Egypt, Io, afterwards identified with Isis, married Telegonus and founded the royal families of Egypt, Phoenicia, Argos and Thebes. The journey to Syria in search of Epaphus was invented to explain the fact that the Phoenician goddess Astarte, who was sometimes represented as horned, was confounded with Io.

Io herself is variously interpreted. She is usually understood to be the moon in the midst of the mighty heaven, studded with stars, represented by Argus. According to others, she is the annual rising of the Nile; the personification of the Ionian race; the mist; the earth. It seems probable that she was a duplicate of Hera (Io [Greek: Boukeros] is Hera [Greek: Boopis]), or a deity in primitive times worshipped under the symbol of a cow, whose worship was superseded by that of Hera; the recollection of this early identity would account for Io being regarded as the priestess of the goddess in later times. Amongst the Romans she was sometimes identified with Anna Perenna. The legend of Io spread beyond Argos, especially in Byzantium and Euboea, where it was associated with the town of Argura. It was a favourite subject among Greek painters, and many representations of it are preserved on vases and wall paintings; Io herself appears as a horned maiden or as the heifer watched by Argus.

See R. Engelmann, _De Ione_ (1868), with notes containing references
to authorities, and his article in Roscher's _Lexikon der Mythologie_;
J. Overbeck, _De Ione, telluris, non lunae, Dea_ (1872); P. W.
Forchhammer, _Die Wanderungen der Inachostochter Io_ (1881), with map
and special reference to Aeschylus's account of Io's wanderings; F.
Durrbach in Daremberg and Saglio's _Dictionnaire des antiquites_; G.
Mellen, _De Ius fabula_ (1901); Wernicke _s.v._ "Argos" in
Pauly-Wissowa's _Realencyclopadie_, ii. pt. i. (1896); J. E. Harrison
in _Classical Review_ (1893, p. 76); Bacchylides xviii. (xix.), with
Jebb's notes.

IODINE (symbol I, atomic weight 126.92), a chemical element, belonging to the halogen group. Its name is derived from Gr. [Greek: ioeides] (violet-coloured), in allusion to the colour of its vapour. It was discovered in 1812 by B. Courtois when investigating the products obtained from the mother-liquors prepared by lixiviating kelp or burnt seaweed, and in 1815 L. J. Gay-Lussac showed that it was an element. Iodine does not occur in nature in the uncombined condition, but is found very widely but sparingly distributed in the form of iodides and iodates, chiefly of sodium and potassium. It is also found in small quantities in sea-water, in some seaweeds, and in various mineral and medicinal springs. Deep-sea weeds as a rule contain more iodine than those which are found in the shallow waters.

Iodine is obtained either from kelp (the ashes of burnt seaweed) or from the mother-liquors obtained in the purification of Chile saltpetre. In the former case the seaweed is burnt in large heaps, care being taken that too high a temperature is not reached, for if the ash be allowed to fuse much iodine is lost by volatilization. The product obtained after burning is known either as _kelp_ or _varec_. Another method of obtaining kelp is to heat the seaweed in large retorts, whereby tarry and ammoniacal liquors pass over and a very porous residue of kelp remains. A later method consists in boiling the weed with sodium carbonate; the liquid is filtered and hydrochloric acid added to the filtrate, when _alginic acid_ is precipitated; this is also filtered off, the filtrate neutralized by caustic soda, and the whole evaporated to dryness and carbonized, the residue obtained being known as _kelp substitute_. The kelp obtained by any of these methods is then lixiviated with water, which extracts the soluble salts, and the liquid is concentrated, when the less soluble salts, which are chiefly alkaline chlorides, sulphates and carbonates, crystallize out and are removed. Sulphuric acid is now added to the liquid, and any alkaline sulphides and sulphites present are decomposed, while iodides and bromides are converted into sulphates, and hydriodic and hydrobromic acids are liberated and remain dissolved in the solution. The liquid is run into the iodine still and gently warmed, manganese dioxide in small quantities being added from time to time, when the iodine distils over and is collected. In the second method it is found that the mother-liquors obtained from Chile saltpetre contain small quantities of sodium iodate NaIO3; this liquor is mixed with the calculated quantity of sodium bisulphite in large vats, and iodine is precipitated:--

2NaIO3 + 5NaHSO3 = 3NaHSO4 + 2Na2SO4 + H2O + I2.

The precipitate is washed and then distilled from iron retorts. Iodine may also be prepared by the decomposition of an iodide with chlorine, or by heating a mixture of an iodide and manganese dioxide with concentrated sulphuric acid. Commercial iodine may be purified by mixing it with a little potassium iodide and then subliming the mixture; in this way any traces of bromine or chlorine are removed. J. S. Stas recommends solution of the iodine in potassium iodide and subsequent precipitation by the addition of a large excess of water, the precipitate being washed, distilled in steam, and dried _in vacuo_ over solid calcium nitrate, and then over solid caustic baryta.

Iodine is a greyish-black shining solid, possessing a metallic lustre and having somewhat the appearance of graphite. Its specific gravity is 4.948 (17 deg./4 deg.). It melts at 114.2 deg. C. and boils at 184.35 deg. C. under atmospheric pressure (W. Ramsay and S. Young). The specific heat of solid iodine is 0.0541 (H. Kopp). Its latent heat of fusion is 11.7 calories, and its latent heat of vaporization is 23.95 calories (P. A. Favre and J. T. Silbermann). The specific heat of iodine vapour at constant pressure is 0.03489, and at constant volume 0.02697. It volatilizes slowly at ordinary temperatures, but rapidly on heating. Iodine vapour on heating passes from a violet colour to a deep indigo blue; this behaviour was investigated by V. Meyer (_Ber._, 1880, 13, p. 394), who found that the change of colour was accompanied by a change of vapour density. Thus, the density of air being taken as unity, Victor Meyer found the following values for the density of iodine vapour at different temperatures:--

T deg. C. 253 450 506 842 1027 1570
Density 8.89 8.84 8.73 6.08 5.75 5.67

This shows that the iodine molecule becomes less complex in structure at higher temperatures.

Iodine possesses a characteristic penetrating smell, not so pungent, however, as that of chlorine or bromine. It is only very sparingly soluble in water, but dissolves readily in solutions of the alkaline iodides and in alcohol, ether, carbon bisulphide, chloroform, and many liquid hydrocarbons. Its solutions in the alkaline iodides and in alcohol and ether are brown in colour, whilst in chloroform and carbon bisulphide the solution is violet. It appears to combine with the solvent (P. Waentig, _Zeit. phys. Chem._, 1909, p. 513). Its chemical properties closely resemble those of chlorine and bromine; its affinity for other elements, however, is as a rule less than that of either. It will only combine with hydrogen in the presence of a catalyst, but combines with many other elements directly; for example, phosphorus melts and then inflames, antimony burns in the vapour, and mercury when heated with iodine combines with it rapidly. It is completely oxidized to iodic acid when boiled with fuming nitric acid. It is soluble in a solution of caustic potash, a dilute solution most probably containing the hypoiodite, which, however, changes slowly into iodate, the change taking place rapidly on warming. When alkali is added to aqueous iodine, followed immediately by either soda water or sodium bicarbonate, most of the original iodine is precipitated (R. L. Taylor, _Jour. Chem. Soc._, 1897, 71, p. 725, and K. J. P. Orton, _ibid._ p. 830). Iodine can be readily detected by the characteristic blue coloration that it immediately gives with starch paste; the colour is destroyed on heating, but returns on cooling provided the heating has not been too prolonged. Iodine in the presence of water frequently acts as an oxidizing agent; thus arsenious acid and the arsenites, on the addition of iodine solution, are converted into arsenic acid and arsenates. A dilute solution of iodine prevents the decomposition of hydrogen peroxide by colloidal platinum (G. Bredig, _Zeit. phys. Chem._, 1899, 31, p. 258; 1901, 37, p. 323).

Iodine finds application in organic chemistry, forming addition products with unsaturated compounds, the combination, however, being more slow than in the case of chlorine or bromine. It rarely substitutes directly, because the hydriodic acid produced reverses the reaction; this can be avoided by the presence of precipitated mercuric oxide or iodic acid, which react with the hydriodic acid as fast as it is formed, and consequently remove it from the reacting system. As a rule it is preferable to use iodine in the presence of a carrier, such as amorphous phosphorus or ferrous iodide or to use it with a solvent. It is found that most organic compounds containing the grouping CH3.CO.C--or CH3.CH(OH).C--in the presence of iodine and alkali give iodoform CHI3.

Hydriodic acid, HI, is formed by the direct union of its components in
the presence of a catalytic agent; for this purpose platinum black is
used, and the hydrogen and iodine vapour are passed over the heated
substance. On shaking up iodine with a solution of sulphuretted
hydrogen in water, a solution of hydriodic acid is obtained, sulphur
being at the same time precipitated. The acid cannot be prepared by
the action of concentrated sulphuric acid on an iodide on account of
secondary reactions taking place, which result in the formation of
free iodine and sulphur dioxide. The usual method is to make a mixture
of amorphous phosphorus and a large excess of iodine and then to allow
water to drop slowly upon it; the reaction starts readily, and the gas
obtained can be freed from any admixed iodine vapour by passing it
through a tube containing some amorphous phosphorus. It is a
colourless sharp-smelling gas which fumes strongly on exposure to air.
It readily liquefies at 0 deg. C. under a pressure of four
atmospheres, the liquefied acid boiling at -34.14 deg. C. (730.4 mm.);
it can also be obtained as a solid melting at -50.8 deg. C. It is
readily soluble in water, one volume of water at 10 deg. C. dissolving
425 volumes of the acid. The saturated aqueous solution is colourless
and fumes strongly on exposure to air; after a time it darkens in
colour owing to liberation of iodine. The gas is readily decomposed by
heat into its constituent elements. It is a powerful reducing agent,
and is frequently employed for this purpose in organic chemistry; thus
hydroxy acids are readily reduced on heating with the concentrated
acid, and nitro compounds are reduced to amino compounds, &c. It is
preferable to use the acid in the presence of amorphous phosphorus,
for the iodine liberated during the reduction is then utilized in
forming more hydriodic acid, and consequently the original amount of
acid goes much further. It forms addition compounds with unsaturated
compounds.

It has all the characteristics of an acid, dissolving many metals with
evolution of hydrogen and formation of salts, called _iodides_. The
iodides can be prepared either by direct union of iodine with a metal,
from hydriodic acid and a metal, oxide, hydroxide or carbonate, or by
action of iodine on some metallic hydroxides or carbonates (such as
those of potassium, sodium, barium, &c.; other products, however, are
formed at the same time). The iodides as a class resemble the
chlorides and bromides, but are less fusible and volatile. Silver
iodide, mercurous iodide, and mercuric iodide are insoluble in water;
lead iodide is sparingly soluble, whilst most of the other metallic
iodides are soluble. Strong heating decomposes the majority of the
iodides. Nitrous acid and chlorine readily decompose them with
liberation of iodine; the same effect being produced when they are
heated with concentrated sulphuric acid and manganese dioxide. The
soluble iodides, on the addition of silver nitrate to their nitric
acid solution, give a yellow precipitate of silver iodide, which is
insoluble in ammonia solution. Hydriodic acid and the iodides may be
estimated by conversion into silver iodide.

Iodine combines with chlorine to form _iodine monochloride_, ICl,
which may be obtained by passing dry chlorine over dry iodine until
the iodine is completely liquefied, or according to R. Bunsen by
boiling iodine with _aqua regia_ and extracting with ether. It exists
in two different crystalline forms, the more stable or [alpha] form
melting at 27.2 deg. C., and the less stable or [beta] form melting at
13.9 deg. C. It is readily decomposed by water. The _trichloride_,
ICl3, results from the action of excess of chlorine on iodine, or from
iodic acid and hydrochloric acid, or by heating iodine pentoxide with
phosphorus pentachloride. It crystallizes in long yellow needles and
decomposes readily on heating into the monochloride and chlorine. It
is readily soluble in water, but excess of water decomposes it. (See
W. Stortenbeker, _Zeit. phys. Chem._, 1889, 3, p. 11.) Iodine
monochloride in glacial acetic acid solution was used by A. Michael
and T. H. Norton (_Ber._, 1876, 9, p. 1752) for the preparation of
paraiodo-acetanilide.

_Iodine Pentoxide_, I2O5, the best-known oxide, is obtained as a white
crystalline solid by heating iodic acid to 170 deg. C.; it is easily
soluble in water, combining with the water to regenerate iodic acid;
and when heated to 300 deg. C. it breaks up into its constituent
elements, (see M. Guichard, _Compt. rend._, 1909, 148, p. 925.) Iodine
dioxide, I2O4, obtained by Millon, and reinvestigated by M. M. P. Muir
(_Jour. Chem. Soc._, 1909, 95, p. 656), is a lemon-yellow solid
obtained by acting on iodic acid with sulphuric acid, oxygen being
evolved. By acting with ozone on a chloroform solution of iodine, F.
Fichter and F. Rohner (_Ber._, 1909, 42, p. 4093) obtained a yellowish
white oxide, of the formula I4O9, which they regard as an iodate of
tervalent iodine, Millon's oxide being considered a basic iodate.

Although _hypoiodous acid_ is not known, it is extremely probable that
on adding iodine or iodine monochloride to a dilute solution of a
caustic alkali, hypoiodites are formed, the solution obtained having a
characteristic smell of iodoform, and being of a pale yellow colour.
It oxidizes arsenites, sulphites and thiosulphates immediately. The
solution is readily decomposed on the addition of sodium or potassium
bicarbonates, with liberation of iodine. The hypoiodite disappears
gradually on standing, and rapidly on warming, being converted into
iodate (see R. L. Taylor, _Jour. Chem. Soc._, 1897, 71, p. 725, and K.
J. P. Orton, _ibid._ p. 830). The peculiar nature of the action
between iodine and chlorine in aqueous solution has led to the
suggestion that the product is a base, i.e. iodine hydroxide.
Tri-iodine hydroxide, I3.OH, is obtained by oxidizing potassium iodide
with sulphuric acid and potassium permanganate (A. Skrabal and F.
Buchter, _Chem. Zeit._, 1909, 33, pp. 1184, 1193).

_Iodic Acid_, HIO3, can be prepared by dissolving iodine pentoxide in
water; by boiling iodine with fuming nitric acid, 6I + 10HNO3 = 6HIO3
+ 10NO + 2H2O; by decomposing barium iodate with the calculated
quantity of sulphuric acid, previously diluted with water, or by
suspending iodine in water and passing in chlorine, I2 + 5Cl2 + 6H2O =
2HIO3+10HCl. It is a white crystalline solid, easily soluble in water,
the solution showing a strongly acid reaction with litmus; the colour,
however, is ultimately discharged by the bleaching power of the
compound. It is a most powerful oxidizing agent, phosphorus being
readily oxidized to phosphoric acid, arsenic to arsenic acid, silicon
at 250 deg. C. to silica, and hydrochloric acid to chlorine and water.
It is readily reduced, with separation of iodine, by sulphur dioxide,
hydriodic acid or sulphuretted hydrogen, thus:--

HIO3 + 5HI = 3H2O + 3I2; 2HIO3+5SO2 + 4H2O = 5H2SO4 + I2;
2HIO3 + 5H2S = I2 + 5S + 6H2O.

The salts, known as the _iodates_, can be prepared by the action of
the acid on a base, or sometimes by the oxidation of iodine in the
presence of a base. They are mostly insoluble or only very slightly
soluble in water. The iodates of the alkali metals are, however,
readily soluble in water (except potassium iodate). They are more
easily reduced than the corresponding chlorates; an aqueous solution
of hydriodic acid giving free iodine and a metallic oxide, whilst
aqueous hydrochloric acid gives iodine trichloride, chlorine, water
and a chloride. They are decomposed on heating, with liberation of
oxygen, in some cases leaving a residue of iodide and in others a
residue of oxide of the metal, with liberation of iodine as well as of
oxygen.

_Periodic Acid_, HIO4.2H2O, is only known in the hydrated form. It can
be prepared by the action of iodine on perchloric acid, or by boiling
normal silver periodate with water: 2AgIO4 + 4H2O = Ag2H3IO6 +
HIO4.2H2O. It is a colourless, crystalline, deliquescent solid which
melts at 135 deg. C., and at 140 deg. C. is completely decomposed into
iodine pentoxide, water and oxygen. The periodates are a very complex
class of salts, and may be divided into four classes, namely,
meta-periodates derived from the acid HIO4; meso-periodates from
HIO4.H2O, para-periodates from HIO4.2H2O and the diperiodates from
2HIO4.H2O (see C. Kimmins, _Jour. Chem. Soc._, 1887, 51, p. 356).

Iodine has extensive applications in volumetric analysis, being used
more especially for the determination of copper.

The atomic weight of iodine was determined by J. S. Stas, from the
analysis of pure silver iodate, and by C. Marignac from the
determinations of the ratios of silver to iodine, and of silver iodide
to iodine; the mean value obtained for the atomic weight being 126.53.
G. P. Baxter (_Jour. Amer. Chem. Soc._, 1904, 26, p. 1577; 1905, 27,
p. 876; 1909, 31, p. 201), using the method of Marignac, obtained the
value 126.985 (O = 16). P. Kothner and E. Aeuer (_Ber._, 1904, 37, p.
2536; _Ann._, 1904, 337, p. 362), who converted pure ethyl iodide into
hydriodic acid and subsequently into silver iodide, which they then
analysed, obtained the value 126.026 (H = 1); a discussion of this and
other values gave as a mean 126.97 (O = 16).

In _medicine_ iodine is frequently applied externally as a counter-irritant, having powerful antiseptic properties. In the form of certain salts iodine is very widely used, for internal administration in medicine and in the treatment of many conditions usually classed as surgical, such as the bone manifestations of tertiary syphilis. The most commonly used salt is the iodide of potassium; the iodides of sodium and ammonium are almost as frequently employed, and those of calcium and strontium are in occasional use. The usual doses of these salts are from five to thirty grains or more. Their pharmacological action is as obscure as their effects in certain diseased conditions are consistently brilliant and unexampled. Our ignorance of their mode of action is cloaked by the term _deobstruent_, which implies that they possess the power of driving out impurities from the blood and tissues. Most notably is this the case with the poisonous products of syphilis. In its tertiary stages--and also earlier--this disease yields in the most rapid and unmistakable fashion to iodides; so much so that the administration of these salts is at present the best means of determining whether, for instance, a cranial tumour be syphilitic or not. No surgeon would think of operating on such a case until iodides had been freely administered and, by failing to cure, had proved the disease to be non-syphilitic. Another instance of this deobstruent power--"alterative," it was formerly termed--is seen in the case of chronic lead poisoning. The essential part of the medicinal treatment of this condition is the administration of iodides, which are able to decompose the insoluble albuminates of lead which have become locked up in the tissues, rapidly causing their degeneration, and to cause the excretion of the poisonous metal by means of the intestine and the kidneys. The following is a list of the principal conditions in which iodides are recognized to be of definite value: metallic poisonings, as by lead and mercury, asthma, aneurism, arteriosclerosis, angina pectoris, gout, goitre, syphilis, haemophilia, Bright's disease (nephritis) and bronchitis.

Small quantities of the iodate (KIO3) are a frequent impurity in
iodide of potassium, and cause the congeries of symptoms known as
_iodism_. These comprise dyspepsia, skin eruption and the
manifestations which are usually identified with a "cold in the head."
In many cases, as in syphilis, aneurism, lead poisoning, &c., the life
of the patient depends on the free and continued use of the iodide,
and this is best to be accomplished by securing an absolutely pure
supply of the salt. Another often successful method of preventing the
onset of symptoms of poisoning is to administer small doses of
ammonium carbonate with the drug, thereby neutralizing the iodic acid
which is liberated in the stomach.