that machicolation, and in late examples a battlemented parapet; whilst the entrance was flanked by strong loopholed towers, and sometimes covered by a barbican, and could only be reached by passing over a draw-bridge. The gate-houses of monasteries were equally large, but less military and more ornamental in character. In some abbey gate-houses the upper chamber was a chapel, in others it was used as a guest-house; occasionally it served as a prison. Alongside the large gateway there was a smaller or postern entrance. Some of the monastic gate-houses were elaborate architectural structures, corresponding to the wealth and rank of the establishment to which they belonged. When the dwellings of the feudal nobles ceased to be fortified, the chief entrance to the great houses continued to be through a gate-house, the abbey gate-house being often taken as the model, as it also was for the gate-houses of colleges. Gate-houses of each class are still numerous in this country. Among the gate-houses of fortresses and castles may be mentioned those at the Tower, London; Chepstow, Warwick, Alnwick, Durham, Carisbrooke; among those of monasteries and cathedrals, Canterbury (and St. Augustine's), Winchester, St. Albans, Evesham, Bury St. Edmunds; whilst both Oxford and Cambridge supply instances of college gate-houses, one of the best of the late examples being that of Trinity College, Cambridge.

GAULTHERIA OIL. Oil of Wintergreen. This, which is the volatile oil of Gaultheria procumbens, consists essentially of methylic salicylate CH ̧ ̧ = {C (C,H30, CHO), SCH2HO mixed with a small quantity of Gaultherilene, a hydrocarbon isomeric with oil of turpentine. Pure gaultherilene is a colourless mobile oil boiling at 160°, and having an odour recalling that of pepper.

days come, saith the Lord, that it shall no more be called Tophet, nor the valley of the son of Hinnom, but the valley of slaughter; for they shall bury in Tophet, till there be no place. And the carcases of this people shall be meat for the fowls of the heaven, and for the beasts of the earth; and none shall fray them away." (Jeremiah vii. 32, 33.) On account of the dreadful associations of the place, whether in the way of crime or of punishment,-from the awful wickedness committed in the valley, perhaps, as much as from the satanic fires kindled in it— the name Gehenna came to be frequently applied, throughout the Gospels and Epistles of the New Testament, to the state of eternal misery which was to follow a life of sin, impenitence, and unbelief; and early in the history of the Church, it was established as a definite locality. "Gehenna," says Justin Martyr, "is a place where those will be punished who have lived unjustly, and who do not believe that those things will happen which God taught through Christ."

GEISSLER TUBES. [ELECTRICAL DISCHARGE IN RAREFIED AIR, E. C. S. col. 847.1

GELATINE. The various modes of obtaining gelatine from skin-parings and hide-clippings [GELATINE AND GLUE, E. C. vol. iv. col. 327] have in some particulars been improved in recent years. Cox's gelatine, made from selected portions of ox and calf hide, undergoes purifying processes which give it great adhesive strength, as well as transparency. Mackay's gelatine, however, whether prepared from hide, skin, muscle, cartilage, as a diet for invalids, is made from calves' feet. In all kinds, ligament, tendon, or membrane, the routine of processes generally includes washing, cutting into small pieces, steeping in some kind of alkaline liquor, and boiling in steam-heated gelatinizing vessels; the gelatine, strained off from the dregs, is cooled in thin layers, cut into pieces, and dried upon nets. If the gelatine is to be coarser or finer than the average, the number of processes is lessened or increased.

Benzile, or coal oil, has recently been used to extract coarse gelatine from any animal substances that will yield glue, by driving out the grease, and allowing the gelatine to fall to the bottom of the vessel; the benzile can be purified for subsequent

use.

GAULTHERILENE. [GAULTHERIA OIL, E. C. S.] GAUNTLET (French Gantelet), a glove covered on the back with plates of metal, which formed part of the full suit of armour worn by knights in the middle ages. The gauntlet appears to have been introduced in the thirteenth century, and its use soon became general. Representations of these early gauntlets frequently occur on monuments and brasses; and the gauntlets themselves of Edward the Black Prince are preserved with his helmet in Canterbury Cathedral. The gauntlet was made of leather of In making bone soup, or bone-gelatine soup, on a large scale, sufficient length to cover the wrist and fore-part of the arm, the as is much done in France, well-planned apparatus is used. To plates on the back of the hand and fingers being made to over-produce 1000 rations per day, four cylinders are used, each capalap, and at the same time allow the hand to open aud close ble of holding 70 lbs. of bones. The bones, bruised or crushed, freely. In the fourteenth century steel knobs or spikes, called are put into a basket or cage within the cylinder; a pipe congads, were rivetted on to the knuckle-plates. In the days of ducts water into the top of the cylinder, while another pipe chivalry a knight in formally challenging an opponent, threw introduces steam at the bottom; overhead is an apparatus for down his gauntlet, and the picking of it up signified the accept- lifting the cages out of the cylinders, while beneath is a vessel ance of the challenge. into which the melted gelatine flows as it is boiled out of the bones. The steam is admitted at a temperature of about 223° F. Each cylinder yields 5 quarts of jelly per hour, by the action of 4 quarts of percolating water and 1 quart of steam-water. When the product is to be stronger or purer than usual, additional precautions are taken in the admission of the water and the outflow of the jelly. It is calculated that 100 lbs. of average butchers' meat contain 20 lbs. of bone, which yield 6 lbs. of dry gelatine (representing much more than this weight in the state of jelly); this gelatine, the French physicians contend, ought not to be wasted, as it usually is, in domestic households.

GEHENNA, or GEHINNOM, the valley of the sons of Hinnom, or of shrieking, was so called after one of its sometime proprietors, or on account of the cruel idolatry of which it was the scene. To this idolatry its alternative name of Tophet, or Topheth, a drum, or betraying, is also referred, the beating of drums having been practised in order to drown the cries of the children who were here caused to pass through the fire in sacrifice to Molech, or Moloch. Thus Milton

"First Moloch, horrid king, besmeared with blood
Of human sacrifice, and parents' tears;
Though, for the noise of drums and timbrels loud,
Their children's cries unheard, that passed through fire
To his grim idol. Him the Ammonite

Worshipped in Rabba and her watery plain,

In Argob and in Basan, to the stream

Of utmost Arnon. Nor content with such

Audacious neighbourhood, the wisest heart

Of Solomon he led by fraud to build

His temple right against the temple of God,
On that opprobrious hill; and made his grove
The pleasant valley of Hinnom, Tophet thence

And black Gehenna called, the type of hell."-(Par. Lost, i. 392.) Gehenna, the modern name of which is Wady Jehennam, is described by Jeremiah as situated "by the entry of the east gate" of Jerusalem; and it is said to have been a very delightful spot, well-watered and well-wooded, and especially as containing a grove consecrated to the idol. The valley of Hinnom has been lately depicted as very deep, shaded by the olive-trees hanging over its precipitous sides, and presenting the appearance of stillness, peace, and beauty. Yet it was here that Manasseh caused his children to pass through the fire to Moloch, and that the people of Judah followed his depraved example. Here also Jeremiah uttered his prophecy of the wars that should follow the abominations of the place:-" Therefore, behold, the

ARTS AND SCI. DIV.-SUP.

Gelatine is now employed in the making of moulds for casts or reproductions of carvings and bassi-rilievi, its elasticity enabling one continuous film to serve for a considerable amount of undercut work. The gelatine, by the use of a clay core or backing, is made to flow over the carving in a nearly equable layer; in twelve hours, when it has attained the consistency of india-rubber, it may be peeled from the surface in one piece, some force being needed to aid this when the undercutting is deep. The gelatine, with a suitable backing, becomes a mould from which casts may be taken.

GELATIO, freezing, a term formerly applied to the rigid state of the body now known as catalepsy.

GELD, from the Anglo-Saxon, geld or gield, money paid as a tribute or for compensation. The word is now obsolete, but it frequently occurs in old law-books in composition, as Danegeld or gelt, the tax or tribute imposed by the Danes; wergeld, the fine or compensation for the slaying of a man; orfgeld, or horngeld, that paid for a beast; angeld, the single value of a thing; twigeld, its double value, and so on. Lands subject to the payment of taxes were frequently termed terræ geldabiles, and the sums paid to the crown were called geldum regis. (Spelman's Glossary; Jacob's Law Dictionary; Du Cange's Glossary under gildum and geldare.)

4 C

GELOSE, a gelatinous principle, which forms the essential constituent of a vegetable substance called Chinese moss, supposed to be obtained from certain lichens growing on trees in the South of China, and in the islands of the Philippine Archipelago. (Payen, Compt. Rend. xlix. 521.)

particularly prized by the Romans. After the emerald comes the beryl, from India, with hexahedral crystals, and of the colour of sea water; of which the varieties were the chrysoberyl, with a yellowish hue; the hyacinthine, and aeroeides, or air-coloured, strung by Indians as cylinders on the hair of an GEM, a word signifying either an engraved stone [ENGRAVED elephant; the Indian opal, of various colours, the sardonyx, STONES, E. C. S. col. 882] or a hard and precious stone, such as much used for camei and cups, and so called from its mixture of is used for jewellery. Such stones appear to have been employed the sard and onyx, brought from Paros, Assos, India, Arabia, amongst the Oriental nations from the earliest period, but more Babylon, Leucadia, and Lesser Armenia. The onyx, so called frequently as engraved signet rings. The Egyptians, however, from its supposed likeness to a finger-nail, coming from Carmade great use of hard and precious stones, in the shape of sphe- mania. The sardonyx had the colour of the chrysolith, sard, and rical, square, lozenge, and cylindrical beads for necklaces; and jasper; it had sometimes as many as seven layers, the lower amongst the materials so employed are the amethyst, the beryl, black or bluish brown. The carbunculus, a fiery transparent Amazon stone, or root of emerald; the jasper, carnelian, chalce- gem, from India, Garamantis, Ethiopia, and Alabanda, perhaps dony, crystal, and lapis lazuli. Necklaces of similar beads have the modern ruby. The amethystine, syrtita, shining with paralso been exhumed on Babylonian and Assyrian sites, but it is ticular colour of which huge vases were made; the Carthaginian, doubtful if they belong to the period of the native monarchies, darker in glow; the Alabandine, darker still, the Thracian, and and are not rather of the Parthian and Sassanian period. At Troezenian, with white spots; Corinthian paler. The Anthe same time it is difficult to conceive that stones, either cut or thracitis, from Thesprotia; the Sanderesius, from India, prized set, were not in use at the time when engraving on hard stones by the Chaldeans. The lychnis, or lamp, a kind of carbunculus, was universal. The Egyptians called the jasper khenem, the from Orthosia, Caria, India, and Ionia, the mines of Nasamones, emerald uat, the turquoise mafka, and the lapis lazuli khesbet. and near Thebes, with electrical qualities, but not so good for Amongst the Greeks hard and precious stones, either for neck-seals as the sard: vases were made of it. The Topazos, which was laces or jewels, are comparatively rare. The earrings of Hera the name of the Topaze, from the Isle of Cytis, or Topazos, off or Juno, and the collar given by Eurymachus to Penelope, are the coast of Arabia, first given by Philemon, a prefect, to Berementioned by Homer; but it is doubtful of what kind of precious nice. A statue of Arsinoe, of four cubits, is said to have been material they were made. Amber, which was not a precious carved of this material. It also was found at Alabastron, near stone, appears from the objects found made of it to have an- Thebes. Varieties were the prasoeides, the chrysopheros, the ciently ranked as a gem, but it was not till a late period that kallais, of a pale green, almost white, which came from India rough or polished stones came into use for jewellery. The and the Caucasus, much used for necklaces; the prasius and Greeks appear to have preferred for this purpose the precious chrysoprasos, poorer kinds, were used for vessels and cylinders. metals. Yet they were early acquainted with different hard and Still more inferior was the Nilion. The Molochites, or malaprecious stones, and had studied their qualities. Herodotus chite, found in Arabia, was used as a charm for children. There mentions the jasper, emerald, and crystal. In the 5th century B.C. were many varieties of the Jaspis, or jasper. The Indian were Onomacritus, under the name of Orpheus, had written a work green, the Cyprian dark green, the Persian air-coloured; the on stones, principally in reference to their virtues, as amulets Caspian, and those of Thermodon blue; the Phrygian_purple ; or talismans. He mentions the supposed virtue of crystal in those of Amisos green; of Chalcedon purple and green. The boria conciliating the gods, and its power as a burning lens. Similar was like a northern sky; the grammaticus, "lined," and polypowers were assigned to the galaktites, anaktites, adamas, and grammaticus, much lined with white lines; the kapnios, or smokey, lethæus, and others to the petrakes, and a stone called the keras all used for camei and gems. The sapphiros, a transparent gem with elaphou, or stagshorn, said to be found in the waters of the gold and blue light, or purple hue from Media. The amethystos, or Euphrates, and another stone called the spring-coloured jasper. amethyst, of the colour of wine, tending to violet, came from India, The lychnis, another transparent stone, he states to be able to set Arabia Petræa, Lesser Armenia, Egypt, Galatia, Thasos, and Cyfire to substances. He also mentions the topazos, the opallion, the prus. The Socondion, a hyacinthine variety, was so called from chrysolith, the magnetis, the ostrites, ophites, gagates, skorpios, Socon, the Indian term for the hyacinth. Some, like crystal, the koryphodes, kuralion, siderites, achales, hæmatites, neurites, Sapenos and Pharanitis, came from Arabia. The Hyacinthus was chabazios, chrysoprasos. At a latter period Plato mentions the only distinguished from the amethyst by its more diluted colour. sard, the jasper, the smaragdos, or emerald, and the adamas, or It came from Ethiopia, the Tibareni, and Arabia. The chrysodiamond, under the name of chrysou-ozos, and the magnet. Aris-lithos, a yellow transparent stone, and the melichrysi, came from totle also wrote a treatise on stones, unfortunately lost, and India. The paederos, or opal, white and green colour; from mentions many precious stones. Theophrastus has left a small Egypt the Tenites; from Arabia the galaktites: it also was treatise on stones, the simple substance or element of which found in Thrace and Cyprus. The Asteria, a white glittering he considered to be earth. He mentions the smaragdos, emerald, stone, reflected the sun's rays, and had an included light like the as the colour of water, found in Cyprus, the anthrax, or carbuncle, cat's eye; it came from Caramania and India. The Astrios, the sapphiros, of large size, used for obelisks and columns at another stone of the same kind, had in it the light of the full moon: Babylon, and coming from Cyprus and Bactria; and the chryso- it came also from Caramania. The keraunia, or lighting stone, colla, allied to the jasper, found in the gold mines at Stoboi. To was a poorer kind; the astrobolos was used for magic; the astroites these he adds the lynkurion, supposed to be a congealed excretion resembled a fish's eye held up to the sun; the iris, so called from of the lynx, with electrical qualities. The anthrakion, omphax, an island in the Red Sea, near Berenice, was like a hexahedral amethyst of the colour of wine, the kyanos, the achates, so called crystal, and reflected prismatic colours. Of the Achates, or agate, from the name of a river in Sicily, but found, although of poorer there was a large family, so called from their resemblance or quality, in Greece, but of finer colour at Carthage, Massalia, union with other stones or colours, as the jaspachates, cerachates, and the Egyptian Katadupai, Syene, and Elephantine; also a smaragdachates, hemachates, leuchates, dendrachates, autachates, kind of black and white stone which he describes as fossil ivory, and the coralloachates, considered sacred and talismanic against a kind of sapphire, and allied to the kyanos. Strabo mentions the bites of scorpions. As at present, likenesses of men and things emeralds and Indian beryls. were traced in the veins of this stone. The Phrygian was green, the Egyptian red from Thebes. Oeta, Lesbos, and Parnassus produced this gem. The akopos, like the niloe, the alabastritis, or alabaster, was from Alabastrum. The alectorion was found in the crops of cocks; the androdamas, with a gleam of silver; the argyrodamas, from Arabia, like ivory; the aromatitis and myrrha, with a fragrant smell; the asbestos, of the colour of iron; the aspilates, from Arabia, of fiery colour. The atizoes, augetis, amphidane, and chrysocolla, like the magnet; the aphrodisiake was white and red; the apsyktos was said when warm to retain heat for seven days. The balanites of Coptos was green, the baptes was white, the" eye of Belus" black, with a white pupil; the baroptenus, or barippe, was black, with sanguineous and white knots; the botryitis was black, like figs or grapes; the bucardia, like a cow's heart, much used in glyphic; the heliotropion, or aethusia, came from Africa and Cyprus, so called

The great work in antiquity on gems is, however, the treatise of the elder Pliny, in his 'Naturalis Historia,' compiled from various Greek and other authors. It mentions six kinds of the adamas, or diamonds-the Cenchron, the Macedonian, from the mines of Philippi; the Cyprian, the Siderites, with the gleam of iron. Next to the diamond in value it classes the pearl; after that the smaragdos, or emerald, of which the hardest variety was the Scythian, the Bactrian, or Indian, the Tanos, or Persian, that of Chalcedon, and the Egyptian, from the mines near Coptos. It mentions a figure of Serapis of this material, several cubits high, evidently not the true emerald; and records Nero looking at the games of the circus through, but more probably at their reflection in, this gem; also the emerald eyes, inlaid in the stone lion of the Cyprian king Hermias, which scared the fishes. This gem was

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AE

GEMS, ARTIFICIAL.

A because when laid in a jarful of water it reflected back the sun's rays with a red colour. The hephastites had the red gleam of a mirror. Other treatises besides that of Pliny have been handed down, as that of Psellus of the 2nd century, and of Marbodus, compiled from that of Evax, an Arabian monarch, contemporary of Tiberius. Another also appeared in the work of Isidorus of Seville, who classes the stones according to their colours.

These later authors, like the Gnostics, attributed mystical virtues to the different stones: thus the sapphire was supposed to conciliate princes and quell enemies; the heliotrope to give prophecy; so the chelonitis; the agate conferred strength. Neither are the ancient derivations accepted by the moderns; nor do the stones bear the same names, which began to change in the middle ages. All the stones described by Pliny cannot be identified. Thus, adamas is supposed to be derived from the Hebrew achlamah or the Persian almas; the iaspis from the Egyptian word for the gem; the sapphiros, or lapis lazuli, from safar, to engrave or shine; the smaragdos, the modern beryl, or aqua marine, from esmarak, a sea monster. The derivation of topazos and beryllus are uncertain; the hyacinthus, or hyacinthine garnet, was so called from the flower; the sapphire, the crystallus, was a quartz crystal; the opalus, the opal; the amethystos, the amethyst; the onyx, an uncoloured agate; the carbunculus was the garnet cut en cabochon; the lychnis was the true ruby; the sandaresius avanturine, or apanturin; the chrysolithus citrine, or yellow quartz; the tanos was Amazon stone, or felspar; the prascius was green jasper; the beryllus aeroeides was a true beryl; the callais the turquoise; the molochites was a peagreen jasper; the topazius, pale yellow chrysolite; the chrysoberyllos a yellowish beryl; the alabandine a garnet; the prasius, an impure translucent quartz. The chalcedony, in its sapphirine, amethystine, The and other varieties, was much used. The Egyptian emerald was a poor stone, although much prized by the Romans. adamas of India was the Carnatic sapphire. The morio was a dark sard which, held up to the light, was transparent red. The green jaspis was a green chlorite and chalcedony. The spinel ruby, a stone much used and prized in the middle ages and the renaissance, derived its name from spinther, a spark.

1126

GEMS, FLUID CAVITIES IN. carbonate of soda, 2 of burnt borax, 1 of saltpetre, 3 of minium, and 12 of the purest white sand. This is combined with other substances, according to the kind of gem to be imitated for sapphire, 10 of carbonate of cobalt; amethyst, 5 carbonate of protoxide of manganese; topaz, 30 oxide of uranium; emerald, 20 protoxide of iron +10 carbonate of copper; opal, 10 oxide M. Gaudin, in a paper read before the French Academy of of cobalt + 15 oxide of manganese + 25 protoxide of iron. Sciences in 1871, describes the result of a series of experiments, a kiln and crucible, to melt the substances experimented on. in which an oxyhydrogen blowpipe was employed, instead of The transparent oxides produced are intermediate in character between true gems and the strass or paste of which artificial gems are ordinarily made. He has not yet produced pure gems Difficulty is experienced in adding the by using alumina alone; he is obliged to add silica, which affects the results. colouring agents, which are not so manageable under the blowpipe as by the heat of a crucible; these agents are various— oxides, chlorides, and salts of gold, silver, palladium, manganese, nickel, and copper-according to the colour and shade to be produced. To whatever extent success may attend the experiments, the results may be regarded as real gems, however imM. Feil, in the same year, exhibited to the same Society perfect, not merely the materials of glass or enamel coloured. rubies, sapphires, and emeralds, made by himself, rich both in tone and in brilliancy. The mode of doing this was suggested Imitative gems for cheap jewellery are usually made in one to him while experimenting on Faraday's heavy optical glass. or other of the modes described in GLASS MANUFACTURE—ArtiGEMS, FLUID CAVITIES IN. Many years ago Sir D. ficial Gems [E. C. vol. iv. col. 395]. Brewster described, in the Transactions of the Royal Society of where, some curious phenomena in connection with cavities in Edinburgh,' in the Edinburgh Journal of Science,' and elsegems containing two different fluids. The interest in the subject has been recently revived, in consequence of the researches of Professor Andrews and others on the continuity of matter. On examining with the microscope the structure of sapphire, [MATTER, LIQUID AND GASEOUS STATE OF, E. C. S.] chrysoberyl, topaz, beryl, quartz, amethyst, peridot, and other minerals, Brewster discovered that there are, in their interior, thousands of cavities of various forms and sizes; some of regular shape, others of very irregular outline, consisting of cavities and branches united without order, but communicating with each other. Some are large enough to be distinguished by the naked eye. Most of them contain two transparent colourless fluids in actual contact without mixing, and one of them expands thirty times more than water, and at about 80° F. fills up the cavity. At low temperatures a vacuity or space filled with gas or vapour exists in the liquid. This disappears at about 80°, and on raising the temperature the fluid quits the sides and an effervescence or rapid ebullition takes place, and the cavity be Care is required in applying comes for a moment opaque, with a large number of minute vacuities which instantly unite into one that goes on enlarging heat, as the mineral has been known to explode with violence. as the temperature diminishes. The heat of the mouth has been sufficient for this. A gentleman put a crystal into his mouth for the purpose of expanding the Brewster supposes such an accident to be fluid. "The specimen burst with great force and cut his mouth, and the fluid which was discharged from the cavity had a very disagreeable taste." far from improbable, even with the heat of the skin, should These cavities have been examined by Messrs. Sorby and the cavity happen to be near the surface or edge of the stone. Butler, and an account of the results, accompanied by a plate of thirteen figures, is given in the 'Proceedings of the Royal Society,' vol. xvii. p. 291. It has also been pointed out by Simmler ('Pogg. An. cv. 460) that the physical properties of the those of liquid carbonic acid than with those of any other known liquid in topaz, as observed by Brewster, agree more nearly with substance. Now liquid carbonic acid, when heated from 0° to 32° C., expands from 100 to 145. In one of Sorby's most relifrom 100 to 150, so that "it seems as if we should be justified in concluding provisionally that it is liquid carbonic acid, which, like water, should be classed among natural liquid mineral substances." Hence if in the formation of the gem, say at a great depth below the surface, gaseous carbonic acid heated and highly compressed were enclosed in growing crystals, it might condense on cooling, so as more or less to completely fill the cavities with the liquid acid. Some of the cavities in emerald contained ap

Under Alexander the Great and his successors, the use of gems, borrowed from the Asiatics, increased amongst the Greeks, especially for inlaying cups and armour. A magnificent candelabrum, enriched with stones of the purest water, was made at Antioch by one of the later Seleucida as a present for the The Caesars and the Empresses temple of Jupiter at Rome. adorned their dresses with precious stones of incalculable value, especially pearls and emeralds. Those of Lollia Paulina, the wife of Caligula, were reckoned at 400,000l. Augustus indulged in the same taste. Stringed instruments were ornamented with gems. Gallienus wore jewelled armour and shoes, as did Elagabalus; and the military decorations called phalerae were inlaid with stones. The figures of the gods, the eyes of statues, litters, chariots, girdles, shields, helmets, were inlaid with them, as were the diadems or crowns of the later Emperors after Constantine I. The Nor did the passion for gems decline under the Emperors of the East and West, and it was transmitted to their successors. crowns of the Gothic Kings of Spain were inlaid with gems, as was the iron crown of Theodolinda, A.D. 616; that of Agiluph, and that of Hungary, presented to Geisa by Michael Ducas, A.D. 1072. In the 8th and 9th centuries book covers were ornamented with carbuncled stones, cut en cabochon; and, in the 12th century, belts, reliquaries, and chalices were so adorned. In the middle ages superstition attributed to them the virtues ascribed by the Roman and Gnostic writers, and added some new ones. The diamond was supposed to resist poison, the balass ruby to repress lust, the crystal to repel evil dreams. The inventories of the middle ages are full of notices of jewelled objects, inlaid with diamonds, rubies, emeralds, and other gems; and two authors, Theophilus the Monk and Benvenuto Cellini, have written on them.

(Krause, Pyrgoteles, 8vo, Halle, 1856; C. W. King, Antique Gems, 8vo, London, 1860; Edinburgh Review, 1866, p. 228; Storey Maskelyne, Gems of the Marlborough Collection, 8vo, Lon-able measurements the liquid in a sapphire cavity expanded don, 1870; Labarthe, Handbook of Medieval Antiquities, 8vo, London, 1856; De Barrera, Gems and Jewels, 8vo, London, 1860.) GEMS, ARTIFICIAL. French and German chemists have recently made numerous researches concerning factitious gems; endeavouring either to obtain real gems by slow chemical action on elementary substances, or to produce mere imitations in coloured glass or enamel. The superintendent of the Berlin Royal Porcelain Works has recommended as a basis 6 parts of

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