Part 36

The curvature occasionally shows itself among horizontal or gently inclined strata in the form of an abrupt inclination, and then an immediate resumption of the previous flat or sloping character. The strata are thus bent up and continue on the other side of the tilt at a higher level. Such bends are called _monoclines_, _monoclinal folds_ or _flexures_, because they present only one fold, or one half of a fold, instead of the two which we see in an arch or trough. The most notable instance of this structure in Britain is that of the Isle of Wight, of which a section is given in fig. 1. The Cretaceous rocks on the south side of the island rapidly rise in inclination till they become nearly vertical. The Lower Tertiary strata follow with a similar steep dip, but rapidly flatten down towards the north coast. Some remarkable cases of the same structure have been brought to light by J.W. Powell in his survey of the Colorado region.

It much more frequently happens that the strata have been bent into arches and troughs, so that they can be seen dipping under the surface on one side of the axis of a fold, and rising up again on the other side. Where they dip away from the axis of movement the structure is termed an _anticline_ or _anticlinal fold_; where they dip towards the axis, it is a _syncline_ or _synclinal fold_. The diagram in fig. 2 may be taken to represent a series of strata (1-17) thrown into an anticline (AA') and syncline (BB'). A section drawn across these folds in the line CD would show the structure given in fig. 3. Here we see that, at the part of the anticlinal axis (A) where the section crosses, bed No. 4 forms the crown of the arch, Nos. 1, 2 and 3 being concealed beneath it. On the east side of the axis the strata follow each other in regular succession as far as No. 13, which, instead of passing here under the next in order, turns up with a contrary dip and forms the centre of a trough or syncline (B). From underneath No. 13 on the east side the same beds rise to the surface which passed beneath it on the west side. The particular bed marked EF has been entirely removed by denudation from the top of the anticline, and is buried deep beneath the centre of the syncline.

Such foldings of strata must always die out unless they are abruptly terminated by dislocations. In the cases given in fig. 2, both the arch and trough are represented as diminishing, the former towards the north, the latter towards the south. The observer in passing northwards along the axis of that anticline finds himself getting into progressively higher strata as the fold sinks down. On the other hand, in advancing southwards along the synclinal axis, he loses stratum after stratum and gets into lower portions of the series. When a fold diminishes in this way it is said to "nose out." In fig. 2 there is obviously a general inclination of the beds towards the north, besides the outward dip from the anticline and the inward dip from the syncline. Hence the anticline noses out to the north and the syncline to the south.

_Simple Folds._--In describing rock-folds special terms have been assigned to certain portions of the fold; thus, the sloping sides of an anticline or syncline are known as the "limbs," "slopes," "flanks" or "members" of the fold; in an anticline, the part X, fig. 3, the angle of the bend, is the "crest" or "crown" (Ger. _Gewolbebiegung_, Fr. _charniere anticlinale_), the corresponding part of a syncline being the "trough-core" or "base," Y, fig. 3 (Ger. _Muldenbiegung_, Fr. _charniere synclinale_). The portion of an anticline which has been removed by denudation is the "aerial arch," dotted in fig. 3. The innermost strata in a fold constitute the "core," arch-core A, fig. 3, or trough-core B, in the same figure. In the majority of folds the bending of the strata has taken place about an "axial plane" (often called the "axis"), which in the examples illustrated in fig. 3 would pass through the points A and B, perpendicularly to the horizontal line CD. In powerfully folded regions the axial planes of the folds are no longer upright; they may be moderately inclined, producing an "inversion," "inverted fold" or "overfold." When the inclination of the axial plane is great a "recumbent overfold" is produced (Fr. _pli couche_, Ger, _liegende Falte_). In a fold of this kind (fig. 4) we have an "arch limb" (a), a middle limb (b) and a floor or "trough limb" (c). X and Y are the upper and lower bends respectively. One of the important functions of a fold is its direction; this of course depends upon the orientation of the axial plane. The crest-line of an anticline or trough-line of a syncline is rarely horizontal for any great distance; its departure from horizontality is designated the "pitch," and the fold is said to pitch (or dip) towards the north, &c. Most simple folds--with the exception of very shallow curvatures of wide area,--when considered in their entirety, are seen to be somewhat canoe-shaped in form. There are three variations of the simple fold dependent upon the position of the limbs, (1) the limbs may tend to diverge as they recede from the crest (fig. 3), sometimes styled an "open anticline"; (2) the limbs may be parallel in "closed" folds (commonly known as isoclinal folding); (3) the limbs may make an open angle or widen out towards the crest (fig. 4). This is known as a fan-shaped fold (Fr. _pli en eventail_, Ger. _Facherfalte_); another variant of the same form is the mushroom fold (Fr. _pli en champignon_). The axial plane is not always extended: it may be so abbreviated that the folding appears to have taken place about a point; anticlines of this type are variously designated "short-anticlines," "_brachyanticlinaux_" or "domes"; similarly, there are "short-synclines," "_brachysynclinaux_" or "cuvettes." The dip in cases of this kind has been described as "qua-qua versal" or "periclinal."

_Complex Folding._--Sometimes a simple fold has been itself subjected to further folding repeated more than once, it is then termed a "refolded fold" (Fr. _pli replie_); fine examples may be observed in the Alps and in other mountain chains. A great regional major fold containing within itself a number of minor "special" or subsidiary folds is described as a "geanticline" (Fr. _structure en eventail compose_), or as a "geosyncline" (Fr. _structure en eventail renverse_). Even folds of lesser magnitude may be highly complex in regions of extreme crustal movement, and may contain smaller folds of the first, second, third or higher order (Fr. _couches gaufrees_ [fig. 5]). In its smaller manifestation, this class of folding passes into "crumpling" or "puckering," where quite a large number of folds may be crowded into a single hand specimen. In "frilling" or "frilled structure" the folds have still smaller amplitude, and in many highly corrugated rocks minute folds are observable with the microscope that do not appear to the unaided eye. When a series of adjacent isoclinal overfolds has passed into a series of thrusts (see FAULT), the so-called "imbricated" structure (Fr. _structure imbriquee_, Ger. _Schuppenstruktur_) is generated. Occasionally crust-blocks resembling "graben" and "horsts" are circumscribed by folds instead of faults; when this is so they have been called respectively "infolded graben" or "overfolded horsts."

The heterogeneous character of great masses of strata has always had a marked influence on the nature of the folding; some beds have yielded much more readily than others, certain beds will be found to be faulted, while those above and below have folded without fracture. In many examples of apparent plasticity it can be shown that this effect has been produced by an infinite number of minute slippings within the rock substance.

The larger rock folds have produced important economic results. For example, in many coal regions the deposits have been conserved in some districts in the synclines or "basins," while they have been removed by denudation from the uplifted anticlines in others. Near the crest of anticlines is commonly an enriched portion of the ground in mineralized districts; and, in the case of water supply, the tilt of the strata determines the direction of the underground flowage. Again, the most convenient site for oil wells is the crest of an anticline or "dome," where an impervious stratum imprisons the gas and oil in a subjacent saturated layer under pressure.

For a discussion of the question of the distribution and arrangement of the great folded regions of the earth's crust, see E. Suess, _Das Antlitz der Erde_, English translation. _The Face of the Earth_, vols. i., ii., iii., iv. (Oxford). See also E. de Margerie and A. Heim, _Les Dislocations de l'ecorce terrestre_ (Zurich, 1888); A. Rothpletz, _Geotektonische Probleme_ (Stuttgart, 1894).

FOLENGO, TEOFILO (1491-1544), otherwise known as Merlino Coccajo or Cocajo, one of the principal Italian macaronic poets, was born of noble parentage at Cipada near Mantua on the 8th of November 1491, From his infancy he showed great vivacity of mind, and a remarkable cleverness in making verses. At the age of sixteen he entered the monastery of Monte Casino near Brescia, and eighteen months afterwards he became a professed member of the Benedictine order. For a few years his life as a monk seems to have been tolerably regular, and he is said to have produced a considerable quantity of Latin verse, written, not unsuccessfully, in the Virgilian style. About the year 1516 he forsook the monastic life for the society of a well-born young woman named Girolama Dieda, with whom he wandered about the country for several years, often suffering great poverty, having no other means of support than his talent for versification. His first publication was the _Merlini Cocaii macaronicon_, which relates the adventures of a fictitious hero named Baldus. The coarse buffoonery of this work is often relieved by touches of genuine poetry, as well as by graphic descriptions and acute criticisms of men and manners. Its macaronic style is rendered peculiarly perplexing to the foreigner by the frequent introduction of words and phrases from the Mantuan patois. Though frequently censured for its occasional grossness of idea and expression, it soon attained a wide popularity, and within a very few years passed through several editions. Folengo's next production was the _Orlandino_, an Italian poem of eight cantos, written in rhymed octaves. It appeared in 1526, and bore on the title-page the new pseudonym of Limerno Pitocco (Merlin the Beggar) da Mantova. In the same year, wearied with a life of dissipation, Folengo returned to his ecclesiastical obedience; and shortly afterwards wrote his _Chaos del tri per uno_, in which, partly in prose, partly in verse, sometimes in Latin, sometimes in Italian, and sometimes in macaronic, he gives a veiled account of the vicissitudes of the life he had lived under his various names, We next find him about the year 1533 writing in rhymed octaves a life of Christ entitled _L'Umanita del Figliuolo di Dio_; and he is known to have composed, still later, another religious poem upon the creation, fall and restoration of man, besides a few tragedies. These, however, have never been published. Some of his later years were spent in Sicily under the patronage of Don Fernando de Gonzaga, the viceroy; he even appears for a short time to have had charge of a monastery there. In 1543 he retired to Santa Croce de Campesio, near Bassano; and there he died on the 9th of December 1544.

Folengo is frequently quoted and still more frequently copied by Rabelais. The earlier editions of his _Opus macaronicum_ are now extremely rare. The often reprinted edition of 1530 exhibits the text as revised by the author after he had begun to amend his life.

FOLEY, JOHN HENRY (1818-1874), Irish sculptor, was born at Dublin on the 24th of May 1818. At thirteen he began to study drawing and modelling at the schools of the Royal Dublin Society, where he took several first-class prizes. In 1835 he was admitted a student in the schools of the Royal Academy, London. He first appeared as an exhibitor in 1839 with his "Death of Abel and Innocence." "Ino and Bacchus," exhibited in 1840, gave him immediate reputation, and the work itself was afterwards commissioned to be done in marble for the earl of Ellesmere. "Lear and Cordelia" and "Death of Lear" were exhibited in 1841. "Venus rescuing Aeneas" and "The Houseless Wanderer" in 1842, "Prospero and Miranda" in 1843. In 1844 Foley sent to the exhibition at Westminster Hall his "Youth at a Stream," and was, with Calder Marshall and John Bell, chosen by the commissioners to do work in sculpture for the decoration of the Houses of Parliament. Statues of John Hampden and Selden were executed for this purpose, and received liberal praise for the propriety, dignity and proportion of their treatment. Commissions of all kinds now began to come rapidly. Fanciful works, busts, bas-reliefs, tablets and monumental statues were in great numbers undertaken and executed by him with a steady equality of worthy treatment. In 1849 he was made an associate and in 1858 a member of the Royal Academy. Among his numerous works the following may be noticed, besides those mentioned above:--"The Mother"; "Egeria," for the Mansion House; "The Elder Brother in Comus," his diploma work; "The Muse of Painting," the monument of James Ward, R.A.; "Caractacus," for the Mansion House; "Helen Faucit"; "Goldsmith" and "Burke," for Trinity College, Dublin; "Faraday"; "Reynolds"; "Barry," for Westminster Palace Yard; "John Stuart Mill," for the Thames embankment; "O'Connell" and "Cough," for Dublin; "Clyde," for Glasgow; "Clive," for Shrewsbury; "Hardinge," "Canning" and "Outram," for Calcutta; "Hon. James Stewart," for Ceylon; the symbolical group "Asia," as well as the statue of the prince himself, for the Albert Memorial in Hyde Park; and "Stonewall Jackson," in Richmond, Va. The statue of Sir James Outram is probably his masterpiece. Foley's early fanciful works have some charming qualities; but he will probably always be best remembered for the workmanlike and manly style of his monumental portraits. He died at Hampstead on the 27th of August 1874, and on the 4th of September was buried in St Paul's cathedral. He left his models to the Royal Dublin Society, his early school, and a great part of his property to the Artists' Benevolent Fund.

See W. Cosmo Monkhouse, _The Works of J.H. Foley_ (1875).

FOLEY, SIR THOMAS (1757-1833), British admiral, entered the navy in 1770, and, during his time as midshipman, saw a good deal of active service in the West Indies against American privateers. Promoted lieutenant in 1778, he served under Admiral (afterwards Viscount) Keppel and Sir Charles Hardy in the Channel, and with Rodney's squadron was present at the defeat of De Langara off Cape St Vincent in 1780, and at the relief of Gibraltar. Still under Rodney's command, he went out to the West Indies, and took his part in the operations which culminated in the victory of the 12th of April 1782. In the Revolutionary War he was engaged from the first. As flag-captain to Admiral John Gell, and afterwards to Sir Hyde Parker, Foley took part in the siege of Toulon in 1793, the action of Golfe Jouan in 1794, and the two fights off Toulon on the 13th of April and the 13th of July 1795. At St Vincent he was flag-captain to the second in command, and in the following year was sent out in command of the "Goliath" (74), to reinforce Nelson's fleet in the Mediterranean. The part played by the "Goliath" in the battle of the Nile was brilliant. She led the squadron round the French van, and this manoeuvre contributed not a little to the result of the day. Whether this was done by Foley's own initiative, or intended by Nelson, has been a matter of controversy (see _Journal of the Royal United Service Institution_, 1885, p. 916). His next important service was with Nelson in the Baltic. The "Elephant" carried Nelson's flag at the battle of Copenhagen, and her captain acted as his chief-of-staff. Ill-health obliged Foley to decline Nelson's offer (made when on the point of starting for the battle of Trafalgar) of the post of Captain of the Fleet. From 1808 to 1815 he commanded in the Downs and at the peace was made K.C.B. Sir Thomas Foley rose to be full admiral and G.C.B. He died while commanding in chief at Portsmouth in 1833.

See J.B. Herbert, _Life and Services of Sir Thomas Foley_ (Cardiff, 1884).

FOLI (FOLEY), ALLAN JAMES (1837-1899), Irish bass singer, was born at Cahir, Tipperary, on the 7th of August 1837; originally a carpenter, he studied under Bisaccia at Naples, and made his first appearance at Catania in 1862. From the opera in Paris he was engaged by Mapleson for the season of 1865, and appeared with much success in various parts. He sang in the first performance of _The Flying Dutchman_ (Daland) in England in 1870, and in the first performance of Gounod's _Redemption_ in 1882. He was distinguished in opera and oratorio alike for his vigorous, straightforward way of singing, and was in great request at ballad concerts. He died on the 20th of October 1899.

FOLIGNO (anc. _Fulginiae_, q.v.), a town and episcopal see of Umbria, Italy, 771 ft. above sea-level, in the province of Perugia, from which it is 25 m. S.E. by rail. Pop. (1901) 9532 (town), 26,278 (commune). It lies in a fertile plain, on the Topino, a tributary of the Tiber; it is almost square in shape and is surrounded by walls. It is a picturesque and interesting town; several of its churches contain paintings by Umbrian masters, notably works by Niccolo di Liberatore (or Niccolo Alunno, 1430-1502), and among them his chief work, a large altar-piece (the predella of which is in the Louvre) in S. Niccolo. The cathedral has a romanesque S. facade of 1133, restored in 1903; the interior was modernized in the 18th century. To the left of the choir is an octagonal chapel by Antonio da Sangallo the younger (1527). In the same piazza as the S. facade is the Palazzo del Governo, erected in 1350, which has a chapel with frescoes by Ottaviano Nelli of Gubbio (1424). S. Maria infra Portas is said to date from the 7th century, but from this period only the columns of the portico remain. Raphael's "Madonna di Foligno," now in the Vatican, was originally painted for the church of S. Anna. The Palazzo Orfini and the Palazzo Deli are two good Renaissance buildings.

Foligno seems to have been founded about the middle of the 8th century A.D. It changed hands often during the wars of the 13th century, and was destroyed by Perugia in 1281. From 1305 to 1439 it was governed by the family of the Trinci as deputies of the Holy See, until in the latter year one of its members went against the church. Pope Eugene IV. sent a force against Foligno, to which the inhabitants opened their gates, and the last of the Trinci, Corrado II., was beheaded. Henceforth Foligno belonged to the states of the church until 1860. It suffered from a severe earthquake in 1832. Foligno is a station on the main line from Rome (via Orte) to Ancona, and is the junction for Perugia. Three miles to the E. is the abbey of Sassovivo with cloisters of 1229, very like those of S. Paolo fuori le Mura at Rome, with pairs of small columns supporting arches, and decorations in coloured mosaic ("Cosmatesque" work). The church has been modernized.

FOLIO (properly the ablative case of the Lat. _folium_, leaf, but also frequently an adaptation of the Ital. _foglio_), a term in bibliography and printing, with reference either to the size of paper employed, or of the book, or to the pagination. In the phrase "in folio" it means a sheet of paper folded once, and thus a book bound up in sheets thus folded is a book of the largest size and is known as a "folio" (see BIBLIOGRAPHY). Similarly, "folio" is one of the sizes of paper adapted to be thus folded (see PAPER). In book-keeping the word is used for a page in a ledger on which the credit and debtor account is written; in law-writing, for a fixed number of words in a legal document, used for measurement of the length and for the addition of costs. In Great Britain, a "folio" is taken to contain 72 words, except in parliamentary and chancery documents, when the number is 90. In the U.S.A. 100 words form a "folio."

FOLIUM, in mathematics, a curve invented and discussed by Rene Descartes. Its cartesian equation is x^3 + y^3 = 3axy. The curve is symmetrical about the line x = y, and consists of two infinite branches asymptotic to the line x + y + a = o and a loop in the first quadrant. It may be traced by giving m various values in the equations x = 3am/(1 + m^3), y = 3am^2 (1 + m^3), since by eliminating m between these relations the equation to the curve is obtained. Hence it is _unicursal_ (see CURVE). The area of the loop, which equals the area between the curve and its asymptote, is 3a/2.

FOLKES, MARTIN (1690-1754), English antiquary, was born in London on the 29th of October 1690. He was educated at Saumur University and Clare College, Cambridge, where he so distinguished himself in mathematics that when only twenty-three years of age he was chosen a fellow of the Royal Society. He was elected one of the council in 1716, and in 1723 Sir Isaac Newton, president of the society, appointed him one of the vice-presidents. On the death of Newton he became a candidate for the presidency, but was defeated by Sir Hans Sloane, whom, however, he succeeded in 1741; in 1742 he was made a member of the French Academy; in 1746 he received honorary degrees from Oxford and Cambridge. In 1733 he set out on a tour through Italy, in the course of which he composed his _Dissertations on the Weights and Values of Ancient Coins_. Before the Society of Antiquaries, of which he was president from 1749 to 1754, he read in 1736 his _Observations on the Trajan and Antonine Pillars at Rome_ and his _Table of English Gold Coins from the 18th Year of King Edward III_. In 1745 he printed the latter with another on the history of silver coinage. He also contributed both to the Society of Antiquaries and to the Royal Society other papers, chiefly on Roman antiquities. He married in 1714 Lucretia Bradshaw, an actress who had appeared at the Haymarket and Drury Lane (see Nichols's Lit. _Anecdot._ ii. 578-598).

For Sir John Hill's attack on Folkes (_Review of the Works of the Royal Soc._, 1751), see D'Israeli, _Calamities and Quarrels of Authors_ (1860), pp. 364-366.