and cellular structure found in the others. So dense and hard | excrescence,' whence their name is derived, causes great diversity is this portion of the "helmet " that Chinese and Malay artists of aspect among them, the possession of prominent eyelashes carve figures on its surface, or cut it transversely into plates, (not a common feature in birds) produces a uniformity of expreswhich from their agreeable colouring, bright yellow with a scarlet sion which makes it impossible to mistake any member of the rim, are worn as brooches or other ornaments. This bird, which family. Hornbills are social birds, keeping in companies, not to is larger than a raven, is also remarkable for its long graduated say flocks, and living chiefly on fruits and seeds; but the bigger tail, having the middle two feathers nearly twice the length species also capture and devour a large number of snakes, while of the rest. Nothing is known of its habits. Its head was the smaller are great destroyers of insects. The older writers figured by George Edwards in the 18th century, but little else say that they eat carrion, but further evidence to that effect had been seen of it until 1801, when John Latham described is required before the statement can be believed. Almost every the plumage from a specimen in the British Museum, and the morsel of food that is picked up is tossed into the air, and then first figure of the whole bird, from an example in the Museum caught in the bill before it is swallowed. They breed in holes at Calcutta, was published by General Hardwicke in 1823 of trees, laying large white eggs, and when the hen begins to (Trans. Linn. Society, xiv. pl. 23). Yet more than twenty sit the cock plasters up the entrance with mud or clay, leaving years elapsed before French naturalists became acquainted only a small window through which she receives the food he with it. brings her during her incarceration.

In the Bucorvinae we have only the genus Bucorvus, or Bucorax as some call it, confined to Africa, and containing at

least two and perhaps more species, distinguishable by their longer legs and shorter toes, the ground-hornbills of English writers, in contrast to the Bucerolinae which are chiefly arboreal in their habits, and when not flying move by short leaps or hops, while the members of this group walk and run with facility. From the days of James Bruce at least there are few African travellers who have not met with and in their narratives more or less fully described one or other of these birds, whose large size and fearless habits render them conspicuous objects.

As a whole the hornbills, of which more than 50 species have been described, form a very natural and in some respects an isolated group, placed by Huxley among his Coccygomorphae. It has been suggested that they have some affinity with the hoopoes (Upupidae), and this view is now generally accepted. Their supposed alliance to the toucans (Rhamphastidae) rests only on the apparent similarity presented by the enormous beak, and is contradicted by important structural characters. In many of their habits, so far as these are known, all hornbills seem to be much alike, and though the modification in the form of the beak, and the presence or absence of the extraordinary

This remarkable habit, almost simultaneously noticed by Dr Mason in Burma, S. R. Tickell in India, and Livingstone in Africa, and since confirmed by other observers, especially A. R. Wallace in the Malay Archipelago, has been connected by A. D. Bartlett (Proc. Zool. Society, 1869, p. 142) with a peculiarity as remarkable, which he was the first to notice. This is the fact that hornbills at intervals of time, whether periodical or irregular is not yet known, cast the epithelial layer of their gizzard, that layer being formed by a secretion derived from the glands of the proventriculus or some other upper part of the alimentary canal. The epithelium is ejected in the form of a sack or bag, the mouth of which is closely folded, and is filled with the fruit that the bird has been eating. The announcement of a circumstance so extraordinary naturally caused some hesitation in its acceptance, but the essential truth of Bartlett's observations was abundantly confirmed by Sir W. H. Flower and especially by Dr J. Murie. These castings form the hen bird's food during her confinement. (A. N.)

HORNBLENDE, an important member of the amphibole group of rock-forming minerals. The name is an old one of German origin, and was used for any dark-coloured prismatic crystals from which metals could not be extracted. It is now applied to the dark-coloured aluminous members of the monoclinic amphiboles, occupying in this group the same position that augite occupies in the pyroxene group. The monoclinic crystals are prismatic in habit with a six-sided cross-section; the angle between the prismfaces (M), parallel to which there are perfect cleavages, is 55° 49'. The colour (green, brown or black) and the specific gravity (3.0-3.3) vary with the amount of iron present. The pleochroism is always strong, and the angle of optical extinction on the plane of symmetry (x in the figure) varies from o° to 37°. The chemical composition is expressed by mixtures in varying proportions of the molecules Ca(Mg,Fe)(SiO3), (Mg,Fe) (Al,Fe)2SiO, and NaAl(SiO3)2. Numerous varieties have been distinguished by special names: edenite, from Edenville in New York, is a pale-coloured aluminous amphibole containing little iron; pargasite, from Pargas near Abo in Finland, a green or bluish-green variety; common hornblende includes the greenish-black and black kinds containing more iron. The dark-coloured porphyritic crystals of basalts are known as basaltic hornblende.

Hornblende occurs as an essential constituent of many kinds 1 Buffon, as was his manner, enlarges on the cruel injustice done to these birds by Nature in encumbering them with this deformity, which he declares must hinder them from getting their food with ease. The only corroboration his perverted view receives is afforded by the observed fact that hornbills, in captivity at any rate, never have any fat about them.

In The Malay Archipelago (i. 213), Wallace describes a nestling hornbill (B. bicornis) which he obtained as " a most curious object, as large as a pigeon, but without a particle of plumage on any part of it. It was exceedingly plump and soft, and with a semi-transparent skin, so that it looked more like a bag of jelly, with head and feet stuck on, than like a real bird.

March 1895. By his wife, who predeceased him, he left several
children, daughters and sons, one of whom, a major in the
artillery, won the Victoria Cross in South Africa in 1900.
His life was written by his daughter, Mrs Fred. Egerton, (1896).
HORNCASTLE, a market-town in the S. Lindsey or Horncastle
parliamentary division of Lincolnshire, England, at the foot of a
line of low hills called the Wolds, at the confluence of the Bain
and Waring streams; the terminus of a branch line of the Great
Northern railway, 130 m. N. from London. Pop. of urban
district (1901) 4038. The church of St Mary is principally
Decorated and Perpendicular, with some Early English remains
and an embattled western tower. Queen Elizabeth's grammar
school was founded in 1562. Other buildings are an exchange,
a court-house and a dispensary founded in 1789. The prosperity
of the town is chiefly dependent on agriculture and its well-known
horse fairs. Brewing and malting are carried on, and there is
some trade in coal and iron.

of igneous rocks, such as hornblende-granite, syenite, diorite, | on the staff of the German emperor during his visits to England hornblende-andesite, basalt, &c.; and in many crystalline in 1889 and 1890. He died, after a short illness, on the 3rd of schists, for example, amphibolite and hornblende-schist which are composed almost entirely of this mineral. Well-crystallized specimens are met with at many localities, for example: brilliant black crystals (syntagmatite) with augite and mica in the sanidine bombs of Monte Somma, Vesuvius; large crystals at Arendal in Norway, and at several places in the state of New York; isolated crystals from the basalts of Bohemia. (L. J.S.) HORN-BOOK, a name originally applied to a sheet containing the letters of the alphabet, which formed a primer for the use of children. It was mounted on wood and protected with transparent horn. Sometimes the leaf was simply pasted against the slice of horn. The wooden frame had a handle, and it was usually hung at the child's girdle. The sheet, which in ancient times was of vellum and latterly of paper, contained first a large cross-the criss-crosse-from which the horn-book was called the Christ Cross Row, or criss-cross-row. The alphabet in large and small letters followed. The vowels then formed a line, and their combinations with the consonants were given in a tabular form. The usual exorcism-" in the name of the Father and of the Sonne and of the Holy Ghost, Amen "-followed, then the Lord's Prayer, the whole concluding with the Roman numerals. The horn-book is mentioned in Shakespeare's Love's Labour's Lost, v. 1, where the ba, the a, e, i, o, u, and the horn, are alluded to by Moth. It is also described by Ben Jonson

The letters may be read, through the horn, That make the story perfect." HORNBY, SIR GEOFFREY THOMAS PHIPPS (1825-1895), British admiral of the fleet, son of Admiral Sir Phipps Hornby, the first cousin and brother-in-law of the 13th earl of Derby, by daughter of Lieut.-General a Burgoyne, commonly distinguished as "Saratoga " Burgoyne, was born on the 20th of February 1825. At the age of twelve he was sent to sea in the flagship of Sir Robert Stopford, with whom he saw the capture of Acre in November 1840. He afterwards served in the flagship of Rear-Admiral Josceline Percy at the Cape of Good Hope, was flag-lieutenant to his father in the Pacific, and came home as a commander. When the Derby ministry fell in December 1852 young Hornby was promoted to be captain. Early in 1853 he married, and as the Derby connexion put him out of favour with the Aberdeen ministry, and especially with Sir James Graham, the first lord of the Admiralty, he settled down in Sussex as manager of his father's property. He had no appointment in the navy till 1858, when he was sent out to China to take command of the "Tribune" frigate and convey a body of marines to Vancouver Island, where the dispute with the United States about the island of San Juan was threatening to become very bitter. As senior naval officer there Hornby's moderation, temper and tact did much to smooth over matters, and a temporary arrangement for joint occupation of the island was concluded. He afterwards commanded the Neptune in the Mediterranean under Sir William Fanshawe Martin, was flag-captain to Rear-Admiral Dacres in the Channel, was commodore of the squadron on the west coast of Africa, and, being promoted to rear-admiral in January 1869, commanded the training squadron for a couple of years. He then commanded the Channel Fleet, and was for two years a junior lord of the Admiralty. It was early in 1877 that he went out as commanderin-chief in the Mediterraean, where his skill in manoeuvring the fleet, his power as a disciplinarian, and the tact and determination with which he conducted the foreign relations at the time of the Russian advance on Constantinople, won for him the K.C.B. He returned home in 1880 with the character of being perhaps the most able commander on the active list of the navy. His later appointments were to the Royal Naval College as president, and afterwards to Portsmouth as commanderin-chief. On hauling down his flag he was appointed G.C.B., and in May 1888 was promoted to be admiral of the fleet. From 1886 he was principal naval aide-de-camp to Queen Victoria, and in that capacity, and as an admiral of the fleet, was appointed

Remains have been found here which may indicate the existence of a Roman village. The manor of Horncastle (Hornecastre) belonged to Queen Edith in Saxon times and was royal demesne in 1086 and the head of a large soke. In the reign of Stephen it apparently belonged to Alice de Cundi, a partisan of the empress Maud, and passing to the crown on her death it was granted by Henry III. to Gerbald de Escald, from whom it descended to Ralph de Rhodes, who sold it to Walter Mauclerc, bishop of Carlisle in 1230. The see of Carlisle retained it till the reign of Edward VI. when it was granted to Edward, Lord Clinton, but was recovered in the following reign. In 1230 Henry III. directed the men of Horncastle to render a reasonable aid to the bishop, who obtained the right to try felons, hold a court leet and have free warren. An inquisition of 1275 shows that the bishop had then, besides the return of writs, the assize of bread and ale and waifs and strays in the soke. Horncastle was a centre of the Lincolnshire rebellion of 1536. Royalist troops occupied the town in 1643, and were pursued through its streets after the battle fought at Winceby. It was never a municipal or parliamentary borough, but during the middle ages it was frequently the residence of the bishops of Carlisle. Its prosperity has always depended largely on its fairs, the great horse fair described by George Borrow in Romany Rye being granted to the bishop in 1230 for the octave of St Lawrence, together with the fair on the feast of St Barnabas. The three other fairs are apparently of later date.

See George Weir, Historical and Descriptive Sketches of the Town adjacent (London, 1820). and Soke of Horncastle in the County of Lincoln and of Several Places

HORN DANCE, a medieval dance, still celebrated during the

September " wakes " at Abbots Bromley, a village on the borders of Needwood Forest, Staffordshire. Six or seven men, each wearing a deer's skull with antlers, dance through the streets, pursued by a comrade who bestrides a mimic horse, and whips the dancers to keep them on the move. The horn-dance usually takes place on the Monday after Wakes Sunday, which is the Sunday next after the 4th of September. Originally the dance took place on a Sunday.

See Strand Magazine for November 1896; also Folk-lore, vol. vi (1896), p. 381.

HORNE, GEORGE (1730-1792), English divine, was born on the 1st of November 1730, at Otham near Maidstone, and received his education at Maidstone school and University College, Oxford. In 1749 he became a fellow of Magdalen, of which college he was elected president in 1768. As a preacher he early attained great popularity, and was, albeit unjustly, accused of Methodism. His reputation was helped by several clever if somewhat wrong-headed publications, including a satirical pamphlet entitled The Theology and Philosophy f Cicero's Somnium Scipionis (1751), a defence of the Hutchinsonians in A Fair, Candid and Impartial State of the Case between Sir Isaac Newton and Mr Hutchinson (1753), and critiques upon William Law (1758) and Benjamin Kennicott (1760) In 1771 he published his well-known Commentary on the Psalms,

specially important product), sash, doors and blinds, leather,
furniture, shoes, white-goods, wire-fences, foundry and machine
shop products, electric motors, and brick and tile. The value
of the factory product in 1905 was $3,162,677, an increase of
within the district of Erwin (then in Ontario county); after
30.1% since 1900. The first settlement here was made in 1790,
1796 it was a part of Canisteo township, and the settlement itself
was formed and named Hornellsville in honour of Judge George
was known as Upper Canisteo until 1820, when a new township
Hornell (d. 1813). The village of Hornellsville was incorporated
in 1852, and in 1888 was chartered as a city; and by act of the
state legislature the name was changed to Hornell in 1906.
See G. H. McMaster, History of the Settlement of Steuben County
(Bath, New York, 1849).

a series of expositions based on the Messianic idea. In 1776 he | and among its manufactures are silk goods (silk gloves being a was chosen vice-chancellor of his university; in 1781 he was made dean of Canterbury, and in 1790 was raised to the see of Norwich. He died at Bath on the 17th of January 1792. His collected Works were published with a Memoir by William Jones in 1799. HORNE, RICHARD HENRY, or HENGIST (1803-1884), English poet and critic, was born in London on New Year's Day 1803. He was intended for the army, and entered at Sandhurst, but receiving no commission, he left his country and joined the Mexican navy. He served in the war against Spain, and underwent many adventures. Returning to England, he became a journalist, and in 1836-1837 edited The Monthly Repository. In 1837 he published two tragedies, Cosmo de Medici and The Death of Marlowe, and in 1841 a History of Napoleon. The book, however, by which he lives is his epic of Orion, which appeared in 1843. It was published originally at a farthing, was widely read, and passed through many editions. In the next year he set forth a volume of critical essays called A New Spirit of the Age, in which he was assisted by Elizabeth Barrett (Mrs Browning), with whom, from 1839 to her marriage in 1845, he conducted a voluminous correspondence. In 1852 he went to Australia in company with William Howitt, and did not return to England until 1869. He received a Civil List pension in 1874, and died at Margate on the 13th of March 1884. Horne possessed extraordinary versatility, but, except in the case of Orion, he never attained to a very high degree of distinction. That poem, indeed, has much of the quality of fine poetry; it is earnest, vivid and alive with spirit. But Horne early drove his talent too hard, and continued to write when he had little left to say. In criticism he had insight and quickness. He was one of the first to appreciate Keats and Tennyson, and he gave valuable encouragement to Mrs Browning when she was still Miss Elizabeth Barrett.

HORNE, THOMAS HARTWELL (1780-1862), English theologian and bibliographer, was born in London on the 20th of October 1780, and was educated at Christ's Hospital, with S. T. Coleridge as an elder contemporary. On leaving school he became clerk to a barrister, but showed a keen taste for authorship. As early as 1800 he published A Brief View of the Necessity and Truth of the Christian Revelation, which was followed by several minor works on very varied subjects. In 1814, having been appointed librarian of the Surrey Institution, he issued his Introduction to the Study of Bibliography. This was followed in 1818 by his long matured work, the Introduction to the Critical Study of the Holy Scriptures, which rapidly attained popularity, and secured for its author widespread fame and an honorary M.A. degree from Aberdeen. In 1819 he received ordination from William Howley, bishop of London, and after holding two smaller livings was appointed rector of the united parishes of St Edmund the King and Martyr, and St Nicolas Acons in London. On the breaking up of the Surrey Institution in 1823, he was appointed (1824) senior assistant librarian in the department of printed books in the British Museum. After the project of making a classified catalogue had been abandoned, he took part in the preparation of the alphabetical one, and his connexion with the museum continued until within a few months of his death on the 27th of January 1862.

Horne's works exceed forty in number. The Introduction, edited by John Ayre and S. P. Tregelles, reached a 12th edition in 1869; but, owing to subsequent advances in biblical scholarship, it fell into disuse.

HORNELL, a city of Steuben county, New York, U.S.A., on the Canisteo river, 90 m. S.E. of Buffalo. Pop. (1890) 10,996; (1900) 11,918, of whom 1230 were foreign-born; (1910 census) 13,617. Hornell is served by the Erie and the Pittsburg, Shawmut & Northern railways; the latter connects at Wayland (20 m. distant by rail) with the Delaware, Lackawanna & Western. railroad. In the city are St Ann's Academy, the St James Mercy Hospital, the Steuben Sanitarium, a public library, and a county court-house-terms of the county court being held here as well as in Bath (pop. in 1905, 3695), the county-seat, and in Corning. Hornell has extensive car shops of the Erie railroad,

HORNEMANN, FREDERICK (f. 1796-1800), German traveller in Africa, was born at Hildesheim. He was a young man when, early in 1796, he offered his services to the African Association of London as an explorer in Africa. By the association he was sent to Göttingen University to study Arabic and otherwise prepare for an expedition into the unknown regions of North Africa from the east. In September 1797 he arrived in Egypt, where he continued his studies. On the invasion of the country by the French he was confined in the citadel of Cairo, to preserve him from the fanaticism of the populace. Liberated by the French, he received the patronage of Bonaparte. On the 5th of September 1798 he joined a caravan returning to the Maghrib from Mecca, attaching himself to a party of Fezzan merchants who accompanied the pilgrims. As an avowed Christian would not have been permitted to join the caravan Hornemann assumed the character of a young mameluke trading to Fezzan. He then spoke, but indifferently, both Arabic and Turkish, and he was accompanied as servant and interpreter by Joseph Freudenburg, a German convert to Islam, who had thrice made the pilgrimage to Mecca. Travelling by way of the oases of Siwa and Aujila, a "black rocky desert" was traversed to Temissa in Fezzan. Murzuk was reached on the 17th of November 1798. Here Hornemann lived till June 1799, going thence to the city of Tripoli, whence in August of the same year he despatched his journals to London. He then returned to Murzuk. Nothing further is known with certainty concerning him or his companion. In Murzuk Hornemann had collected a great deal of trustworthy information concerning the peoples and countries of the western Sahara and central Sudan, and when he left Tripoli it was his intention to go direct to the Hausa country, which region he was the first European definitely to locate. "If I do not perish in my undertaking," he wrote in his journal, "I hope in five years I shall be able to make the Society better acquainted with the people of whom I have given this short description." The British consul at Tripoli heard from a source believed to be trustworthy that about June 1803 Jusef (Hornemann's Mahommedan name) was at Caśna, i.e. Katsena, in Northern Nigeria, "in good health and highly respected as a marabout." A report reached Murzuk in 1819 that the traveller had gone to "Noofy" (Nupe), and had died there. Hornemann was the first European in modern times to traverse the north-eastern Sahara, and up to 1910 no other explorer had followed his route across the Jebel-esSuda from Aujila to Temissa.

The original text of Hornemann's journal, which was written in German, was printed at Weimar in 1801; an English translation, Travels from Cairo to Mourzouk, &c., with maps and dissertations by Major James Rennell, appeared in London in 1802. A French translation of the English work, made by order of the First Consul, L. Langlès, was published in Paris in the following year. The French and augmented with notes and a memoir on the Egyptian oases by version is the most valuable of the three. Consult also the Proceedings of the African Association (1810), and the Geog. Jnl. Nov. 1906.

HORNER, FRANCIS (1778-1817), British economist, was born at Edinburgh on the 12th of August 1778. After passing through the usual courses at the high school and university of his native city, he devoted five years, the first two in England, to comprehensive but desultory study, and in 1800 was called to the Scottish bar. Desirous, however, of a wider sphere, Horner removed to London in 1802, and occupied the interval

1864.

See Memoir of Leonard Horner, by Katherine M. Lyell (1890) (privately printed).

that elapsed before his admission to the English bar in 1807 | alluvial lands of Egypt; and in 1843 he published his Life of with researches in law, philosophy and political economy. his brother Francis. He died in London on the 5th of March In February 1806 he became one of the commissioners for adjusting the claims against the nawab of Arcot, and in November entered parliament as member for St Ives. Next year he sat for Wendover, and in 1812 for St Mawes, in the patronage of the marquis of Buckingham. In 1811, when Lord Grenville was organizing a prospective ministry, Horner had the offer, which he refused, of a treasury secretaryship. He had resolved not to accept office till he could afford to live out of office; and his professional income, on which he depended, was at no time proportionate to his abilities. His labours at last began to tell upon a constitution never robust, and in October 1816 his physicians ordered him to Italy, where, however, he sank under his malady. He died at Pisa, on the 8th of February 1817. He was buried at Leghorn, and a marble statue by Chantrey was erected to his memory in Westminster Abbey.

Without the advantages of rank, or wealth, or even of genius, Francis Horner rose to a high position of public influence and private esteem. His special field was political economy. Master of that subject, and exercising a sort of moral as well as intellectual influence over the House of Commons he, by his nervous and earnest rather than eloquent style of speaking, could fix its attention for hours on such dry topics as finance, and coinage, and currency. As chairman of the parliamentary committee for investigating the depreciation of bank-notes, for which he moved in 1810, he extended and confirmed his fame as a political economist by his share in the famous Bullion Report. It was chiefly through his efforts that the paper-issue of the English banks was checked, and gold and silver reinstated in their true position as circulating media; and his views on free trade and commerce have been generally accepted at their really high value. Horner was one of the promoters of the Edinburgh Review in 1802. His articles in the early numbers of that publication, chiefly on political economy, form his only literary legacy.

See Memoirs and Correspondence of Francis Horner, M.P., published by his brother (see below) in 1843. Also the Edinburgh and Quarterly Reviews for the same year; and Blackwood's Magazine, vol. i.

HORNER, LEONARD (1785-1864), Scottish geologist, brother of Francis Horner (above), was born in Edinburgh on the 17th of January 1785. His father, John Horner, was a linen merchant in Edinburgh, and Leonard, the third and youngest son, entered the university of Edinburgh in 1799. There in the course of the next four years he studied chemistry and mineralogy, and gained a love of geology from Playfair's Illustrations of the Huttonian Theory. At the age of nineteen he became a partner in a branch of his father's business, and went to London. In 1808 he joined the newly formed Geological Society and two years later was elected one of the secretaries. Throughout his long life he was ardently devoted to the welfare of the society; | he was elected president in 1846 and again in 1860. In 1811 he read his first paper "On the Mineralogy of the Malvern Hills" (Trans. Geol. Soc. vol. i.) and subsequently communicated other papers on the "Brine-springs at Droitwich," and the "Geology of the S.W. part of Somersetshire." He was elected F.R.S. in 1813. In 1815 he returned to Edinburgh to take personal superintendence of his business, and while there (1821) he was instrumental in founding the Edinburgh School of Arts for the instruction of mechanics, and he was one of the founders of the Edinburgh Academy. In 1827 he was invited to London to become warden of the London University, an office which he held for four years; he then resided at Bonn for two years and pursued the study of minerals and rocks, communicating to the Geological Society on his return a paper on the "Geology of the Environs of Bonn," and another "On the Quantity of Solid Matter suspended in the Water of the Rhine." In 1833 he was appointed one of the commissioners to inquire into the employment of children in the factories of Great Britain, and he was subsequently selected as one of the inspectors. In later years he devoted much attention to the geological history of the

HÖRNES, MORITZ (1815-1868), Austrian palaeontologist, was born in Vienna on the 14th of July 1815. He was educated in the university and graduated Ph.D. He then became assistant in the Vienna mineralogical museum. He was distinguished for his researches on the Tertiary mollusca of the Vienna Basin, and on the Triassic mollusca of Alpine regions. Most of his memoirs were published in the Jahrbuch der K. K. geol. Reichsanstall. In 1864 he introduced the term Neogene to include Miocene and Pliocene, as these formations are not always to be clearly separated: the fauna of the lower division being subtropical and gradually giving place in the upper division to Mediterranean forms. He died in Vienna on the 4th of November 1868. His son Dr Rudolf Hörnes (b. 1850), professor of geology and palaeontology in the university of Graz, has also carried on researches among the Tertiary molluscą, and is author of Elemente der Palaeontologie (1884).

HORNFELS (a German word meaning hornstone), the group designation for a series of rocks which have been baked and indurated by the heat of intrusive granitic masses and have been rendered massive, hard, splintery, and in some cases exceedingly tough and durable. Most hornfelses are fine-grained, and while the original rocks (such as sandstone, shale and slate, limestone and diabase) may have been more or less fissile owing to the presence of bedding or cleavage planes, this structure is effaced or rendered inoperative in the hornfels. Though they may show banding, due to bedding, &c., they break across this as readily as along it; in fact they tend to separate into cubical fragments rather than into thin plates. The commonest hornfelses (the "biotite hornfelses") are dark-brown to black with a somewhat velvety lustre owing to the abundance of small crystals of shining black mica. The "lime hornfelses" are often white, yellow, pale-green, brown and other colours. Green and darkgreen are the prevalent tints of the hornfelses produced by the alteration of igneous rocks. Although for the most part the constituent grains are too small to be determined by the unaided eye, there are often larger crystals of garnet or andalusite scattered through the fine matrix, and these may become very prominent on the weathered faces of the rock.

The structure of the hornfelses is very characteristic. Very rarely do any of the minerals show crystalline form, but the small grains fit closely together like the fragments. of a mosaic; they are usually of nearly equal dimensions and from the resemblance to rough pavement work this has been called pflaster structure or pavement structure. Each mineral may also enclose particles of the others; in the quartz, for example, small crystals of graphite, biotite, iron oxides, sillimanite or felspar may appear in great numbers. Often the whole of the grains are rendered semi-opaque in this way. The minutest crystals may show traces of crystalline outlines; undoubtedly they are of new formation and have originated in site. This leads us to believe that the whole rock has been recrystallized at a high temperature and in the solid state, so that there was little freedom for the mineral molecules to build up wellindividualized crystals. The regeneration of the rock has been sufficient to efface most of the original structures and to replace the former minerals more or less completely by new ones. But crystallization has been hampered by the solid condition of the mass and the new minerals are formless and have been unable to reject impurities, but have grown around them.

Slates, shales and clays yield biotite hornfelses in which the most conspicuous mineral is black mica, in small scales which under the microscope are transparent and have a dark reddishbrown colour and strong dichroism. There is also quartz, and often a considerable amount of felspar, while graphite, tourmaline and iron oxides frequently occur in lesser quantity. In these biotite hornfelses the minerals, which consist of aluminium silicates, are commonly found; they are usually andalusite and