IRIARTEA, ir'i-är'tê-a (Neo-Lat., named in honor of Juan de Iriarte, a Spanish amateur botanist). A genus of South American palms which have lofty, smooth, faintly ringed stems, and pinnate leaves with somewhat triangular leaflets. The pashiuba or paxiuba palm (Iriartea exorrhiza, by some botanists called Socratea exorrhiza), common in low, wet grounds in the forests of the Amazon district, is remarkable for its aërial roots, which extend from the stem obliquely downward, and often divide into many rootlets just before they reach the soil. As the tree grows it produces new roots from higher points. Since the older and more central ones die, a man may walk erect with a palm of 70 feet high supported as on legs rising straight above his head. The outer wood, which is very hard, is used for harpoons. It splits easily into straight laths, is excellent for floors, ceilings, shelves, etc., and is exported for umbrella-sticks. The leaves are extensively used in Brazil as thatch.

IRIDACEÆ, ir'i-dā'sê-ē (Neo-Lat. nom. pl., from Lat. iris, Gk. Ipes, rainbow, sort of lily), or IRIS FAMILY. An order of monocotyledonous plants, consisting mostly of herbaceous perennials, with tubers or rhizomes. The leaves are usually in two rows and equitant (i.e. so placed that one seems to fit over the back of the other). The perianth is six-parted, colored, and in some kinds very beautiful. The stamens are three with anthers turned outward. The ovary is inferior with one style and three stigmas, which are often petal-like and add much to the beauty of the flower. The fruit is a three-celled capsule containing many seeds with small embryos in a hard endosperm. There are about 60 genera and 800 species known in temperate and tropical countries. South Africa and tropical America contain the greatest number. Some species, how ever, range to rather high latitudes. Familiar examples of the order are the garden irises, crocuses, gladioli, etc. Some species have acrid properties, while the corms of others are edible, and others have medicinal properties of considerable value. The classification by Pax, with the principal genera, is as follows: Crocoidea, represented by Crocus and Romulea; Iridoideæ, with Iris, Morea, Tigridia, and Sisyrinchium as the leading genera; and Ixoideæ, represented by Ixia, Tritonia, Gladiolus, and Freesia. See Colored Plates of IRIS FAMILY and FLEURS-DE-LIS.

IRIDESCENT GLASS (from Lat. iris, Gk. Ipis, iris, rainbow). Glass containing a display of changing colors on the surface somewhat similar to the delicate hues of soap-bubbles. It is produced by rendering the surface of the glass imperceptibly uneven, either by artificial means or by the natural process of incrustation and decay. One form of treatment consists in applying to the surface of the glass to be treated a strong solution of hydrochloric acid under pressure in a closed vessel. Another method in use in many factories is to apply the fumes from chloride of tin or other chlorides volatilized in a reheating furnace. Glass which has for many years been submitted to the slowly disintegrat ing influences of natural causes, such as damp; successive heat and cold, light and darkness, will in many instances display an iridescent play of colors. The cause is due to a process of decomposition in the texture of the glass, resulting

in the formation of minute scales. The action of water on glass has a tendency to extract the potash and soda which enter into its composition, together with a portion of the silica, the decomposition taking place with greater ease in proportion as the glass is richer in these alkalies, and more minutely divided, and the temperature of the water higher. The moisture in the atmosphere produces a similar alteration in the lapse of time. It separates the potash and soda, leaving the greater part of the silica with the lime on the surface of the glass. It is this decomposition which causes the prismatic colors. If subjected to heat, numerous fine scales will peel off and leave the surface dull, opaque, and wrinkled. Many attempts have been made to imitate by artificial means the singular display of changing hues, and varied success has attended the efforts. In Venice the workers succeeded in giving the surface of their glassware a peculiar kind of metallic iridescence, and a similar result was reached by certain Hungarian glass-workers. New York has a most striking iridescent play The beautiful Favrile Glass made by Tiffany of

of color. See GLASS.

IRIDIUM (Neo-Lat., from Gk. Ips, iris, rainbow; so called on account of its iridescence). A metallic element discovered in 1803 by Smithson Tennant. It is found in platinum ores; as iridosmine, a native alloy of iridium and osmium in varying proportions; and in the form of native alloys with the other platinum metals. The principal sources of these ores are various districts in the Ural Mountains, and on the Pacific Coast of the United States. The preparation of metallic iridium involves its separation from the accompanying metals by a long and conplicated process.

Iridium (symbol Ir; atomic weight, 193.5) is a white steel-like metal, brittle when cold, and somewhat malleable at a white heat. In its ordinary, compact form, iridium is insoluble not only in the several mineral acids, but also in aqua regia; the latter reagent, however, dissolves iridium powder, which may also be converted into the oxide Ir.O, by heating in the air. Iridium has a specific gravity of 22.4, and it melts at 2300° C. It combines with oxygen to form an iridium sesquioxide and an iridium dioxide, which in turn give rise to iridious and iridic salts. The metal itself alloys with copper, gold, and lead, as well as with other platinum metals, and the alloy consisting of nine parts of plati num with one part of iridium is extremely hard, as elastic as steel, perfectly unalterable in the air, and capable of taking a high polish. It is of this alloy that the standard meter kept in Paris was made. Iridium is also used for the manufacture of standard weights, knife edges of balances, and for other articles which it is desired to preserve from the influence of the atmosphere. It has been used in the United States to tip the edges of gold and other as to produce a very hard surface. pens so William L. Dudley of Cincinnati invented a of this material, and his process is now success. process, in 1880, for the electrolytic deposition fully used for coating surgical instruments and other articles requiring an exceedingly hard sur

face.

IR'IDOS/MINE (from irid-ium + osmium). A native alloy of iridium and osmium that

crystallizes in the hexagonal system. It is tinwhite to light steel-gray in color, and has a metallic lustre. The proportions of iridium and osmium in it vary, and other platinum metals, such as platinum, rhodium, and ruthenium, are frequently present. The mineral occurs with platinum minerals in the Ural Mountains, in the auriferous drifts and sands in New South Wales, and in northern California.

IRIGA, ê-rē gå. A town of Luzon, Philippines, in the Province of South Camarines (Map: Philippine Islands, H 6). It lies about 22 miles southeast of Nueva Cáceres, and has a population (1898) of about 17,100.

I'RIS (Lat., from Gk. 'Ipis). In Hesiod, the daughter of Thaumas and Electra, and sister of the Harpies (q.v.). In the Homeric poems she is the virgin messenger of the gods; but Alcæus and later writers state that she was the wife of Zephyrus and the mother of Eros. She is frequently represented on vases and in bas-reliefs as a youthful winged virgin, with a herald's staff. The name in Greek means 'rainbow,' and though Vergil is the first writer to represent the bow as the path of the goddess, there can be no doubt of their original connection. It may be noted that to the Greeks the rainbow was a divine portent, presaging war or heavy rain. Consult: Mayer, "Iris," in Roscher, Lexikon der griechischen und römischen mythologie (Leipzig, 1890-94).-Iris is also the name of one of the planetoids (q.v.), discovered in 1847.

IRIS (Lat., from Gk. Ips, rainbow, sort of lily), or FLOWER-DE-LUCE. A genus of plants of the natural order Iridaceæ, having the three outer segments of the perianth reflexed, the three inner arched inward. and three petal-like stigmas covering the stamens. The species are chiefly natives of temperate climates, especially of North America and Europe. The yellow iris, or corn-flag (Iris Pseudacorus), is a well-known native of moist grounds in many parts of Europe, often spreading over a considerable extent of land, and conspicuous even at a distance by its tall leaves and large, deep-yellow flowers. It is also established in a few places in the Eastern United States. The stinking iris (Iris fœtidissima) a species with livid purple flowers and ill-smelling leaves, is very abundant in the south of England, but does not extend far north. The flowers of most of the species are beautiful. Some of them have received much attention from florists, particularly Iris xiphium, sometimes called Spanish iris; Iris xiphioides, or English iris; and Iris germanica, or common iris, all European corm-rooted species, and the Japanese irises, which probably are well referable to Iris lævigata. Many fine varieties have been produced. The Persian iris (Iris persica) is delightfully fragrant; the snake's-head iris (Iris tuberosa) and the Chalcedonian iris (Iris Susiana) are also much esteemed. The roots of all these species are annually exported in considerable quantities from Holland. Many other species are of frequent occurrence in flowergardens, such as Iris reticulata and Iris atrofusca. The fresh rootstocks of Iris Pseudacorus are very acid. Those of Iris florentina, Iris pallida, and Iris germanica are orris-root (q.v.). Some species have edible rootstocks. Iris versicolor, the large blue flag, is common in wet places through the United States as far

west as Minnesota and Arkansas. Iris cristata is a dwarf species with fragrant flowers found in several localities, and Iris verna and Iris lacustris are other dwarf American species, all of which are cultivated as border plants to a considerable extent. See IRIDACEE and accompanying Colored Plates.

IRIS (Gk. ipis, iris). A term used in anatomy to denote the thin circular curtain, pierced by the pupil, which hangs in the anterior chamber of the eye in front of the crystalline lens. It is attached by its peripheral margin to the sclera, and its posterior surface is pigmented. See EYE; VISION; IRITIS.

IRIS FAMILY. A family of plants. See IRIDACE..

IRISH ACADEMY, ROYAL. A learned association in Dublin, Ireland, incorporated in 1786, with the object of promoting the study of science, polite literature, and antiquities. It is governed by a council consisting of twenty-one members divided into three committees, viz. the Committee of Science, the Committee of Polite Literature, and the Committee of Antiquities. The meetings of the council are distinct from those of the Academy at large, and are held every month from November to June. The library contains a collection of Irish manuscripts, in themselves invaluable, besides papers of public interest, including those of the Ordnance Survey of Ireland. Its collection of Irish antiquities now on exhibition in the National Museum, Dublin, under the Science and Art Departments of the Academy, is both interesting and important.

IRISH CATHOLIC BENEVOLENT UNION. A fraternal and benevolent organization, founded at Dayton, Ohio, in 1869, for social and beneficial purposes. Membership in the union is confined to those who are of Irish extraction, and who are members of the Roman Catholic Church. Since the organization of the union, the sum of $2,124,209 has been disbursed to the beneficiaries of deceased members, and during the fiscal year of 1901-02 the benefits disbursed amounted to $45,371.71. The number of subordinate societies in the union is 149, with a total membership of 13.623.

IRISH DEER. See DEER; ELK.

IRISH LAND LAWS. The land tenure of Ireland is the product of two distinct systems, the Irish tribal and the English feudal. In the former, as described in the Brehon laws, the land was ultimately the property of one of the four or five tribes into which the Irish population was divided. A portion of this land was set aside for the chief or king of the tribe, but by far the greater part of it belonged to the different clans of which the tribes were composed. The clan lands were subdivided among the septs, which were the lowest social units. Land was set aside both for the chiefs of the clans and the chiefs of the septs. The greater part of the sept land, however, was held by the free tribesmen, who owed both rents and military service to their immediate chiefs. These tribesmen held their lands by different kinds of free tenure. The Ceil had herds of cattle (the chief wealth of the country) of his own, while to the Saer and the Daer tenants cattle were lent by the chief. Besides these there were servile tenants (the Fuidhir), who were not original