YAROSLAV, grand duke of Russia. See SIA, vol. xiv., p. 489.

YARRELL, William, a British naturalist, born in St. James's, Westminster, in June, 1784, died in Yarmouth in September, 1856. He was a newspaper agent, and became a naturalist from being a sportsman. In 1824 he was chosen a member of the Linnæan society, and henceforth constantly contributed to its "Transactions" and to other periodical publications on natural history. He was one of the first members of the zoological society, and contributed 17 papers to the first volume of its transactions. Although self-taught, his anatomical descriptions are remarkable for their accuracy. He was the first to prove that the whitebait is a distinct species of fish, and not the young of the shad or herring. Besides about 70 monographs, he wrote "The History of British Fishes" (2 vols. 8vo, 1835-'6; supplement, 1839; 3d ed., with a memoir, 1859), and "The History of British Birds" (3 vols., 1839-'43; 3d ed., 1856). These works contain interesting descriptions and wood engravings of all the species of British birds and fishes. YARROW (A. 9. gearwe), the common name for Achillea millefolium, a plant of the composite family, sometimes called milfoil, introduced from Europe, where, as well as in nearly all parts of this country, it is a common weed, especially around settlements. The genus Achillea

belongs to the same subfamily with chamomile, wormwood, tansy, and other strong - smelling composites, and contains a large number of species; the one known as yarrow is a perennial, with a creeping rootstock; the plant appears in spring as a flat dense cluster, 6 to 12 in. across, of finely and beautifully dissected leaves; later in the season there rise from the centre of this simple leafy stems, bearing at the top a dense terminal flat-topped corymb of small white flowers; the few rays are toothed at the apex, and are fertile, as are the whitish disk flowers. Occasionally the flowers are tinged pinkish, and sometimes a deep rose

Yarrow (Achillea millefolium).

YARROW, a river of Selkirkshire, Scotland, which rises at Yarrow Cleugh, 11 m. E. of Loch Skene, and pursues a general E. N. E. course of 25 m., flowing through Lochs Lowes and St. Mary, and uniting with the Ettrick, a tributary of the Tweed, 1 m. above Selkirk. Its current is fierce and precipitous. On its banks are the ruins of Newark castle, and Bowhill, the seat of the duke of Buccleuch. It receives about 40 small tributaries.

YASSY. See JASSY.

YATES, a W. county of New York, bounded E. by Seneca lake, and S. W. partly by Canandaigua and Crooked (now Keuka) lakes, the latter extending half way across the middle of the county; area, about 500 sq. m.; pop. in 1870, 19,595; in 1875, 19,686. The surface is generally undulating or hilly, and the soil is a fertile sandy loam. Iron ore is found. The county is intersected by the Northern Central railroad, and by the Crooked Lake canal. The chief productions in 1870 were 414,869 bushels of wheat, 28,375 of rye, 337,983 of Indian corn, 507,165 of oats, 354,067 of barley, 30,608 of buckwheat, 169,692 of potatoes, 670,272 lbs. of butter, 41,614 of cheese, 402,176 of wool, and 39,575 tons of hay. There were 6,692 horses, 6,511 milch cows, 6,491 other cattle, 74,439 sheep, and 5,656 swine; 5 manufactories of agricultural implements, 3 of bricks, 23 of carriages and wagons, 11 of saddlery and harness, 5 flour mills, 2 distilleries, 3 planing mills, and 7 saw mills. Capital, Penn Yan.

YATES, Edmund Hodgson, an English novelist, born in July, 1831. He is the son of an actor, and was for several years employed in the London post office as chief of the missingletter department, retiring in 1872. He has been editor of "Our Miscellany," "Temple Bar," and "Tinsley's" magazines, and now (1876) edits the "World" newspaper. In 1872-3 he lectured in the United States. He has published "My Haunts and their Frequenters (1854); "After Office Hours (1861); "Broken to Harness" (1864); "Pages in Waiting," "Running the Gauntlet," and "The Business of Pleasure" (1865); "Land at Last" and "Kissing the Rod" (1866); "The Forlorn Hope" and "Black Sheep" (1867);

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"The Rock Ahead" (1868); "Wrecked in Port" (1869); Dr. Wainwright's Patient" (1870); Nobody's Fortune (1871); and "The Impending Sword" (1874). With F. E. Smedley he wrote "Mirth and Metre, by Two Merry Men" (1854). He has also written some dramas, and was for six years theatrical critic of the "Daily News."

YATES, William, an English missionary, born at Loughborough, Leicestershire, Dec. 15, 1792, died at sea, July 3, 1845. He studied at Bristol college, and sailed for Calcutta, April 16, 1815, as a Baptist missionary. He settled at Serampore, where after the death of Dr. Carey he devoted himself entirely to translating and to preparing text books. He visited England and America in 1827-'9; and in 1845 he embarked for England on account of his health, but died on the passage up the Red sea. He translated the whole Bible into Bengalee; the New Testament and most of the Old into Sanskrit; and the New Testament into Hindee and Hindostanee. Among his most important works are: "Grammar of the Sanskrit Language" (Calcutta, 1820); "Sanskrit Vocabulary" (1820); "Essay on Sanskrit Alliteration;" "Introduction to the Hindostani Language" (in 3 parts, 1827); "Hindostani and English Dictionary" (1836); and "Biblical Apparatus" (in 4 parts, 1837). After his death was published from his manuscript an "Introduction to the Bengali Language," edited by J. Wenger (2 vols., 1847; reprinted under the title "Bengali Grammar," 1864).

YAUPON, an aboriginal name for ilex cassine, a North American shrub which derives its specific name from cassena, by which it was also known to the Indians. The characters of the genus ilex are given under HOLLY, this species, like that, belonging to the section with evergreen leaves. It is a slender shrub growing 8 to 12, and sometimes 15 ft. high, with short, spreading branches, which often terminate in a sharp point or spine, on which account it has been proposed as a hedge plant. The leaves, seldom over an inch long, are oval or oblong, obtuse, thick and shining, but without the large spiny teeth of those of the holly, the margins being merely scalloped by small rounded serratures; the flowers and abundant scarlet fruit much as in the holly. This species is found in light sandy soils from Virginia to Florida, and never at any great distance from the coast; it has proved to be hardy as far north as Philadelphia, and is worthy of cultivation as an ornamental shrub wherever it will endure the winters. The Indians held it in high esteem, and the early travellers in the Carolinas mention its leaves as an article of considerable traffic between the coast tribes and those living further inland. An infusion of the slightly roasted leaves produces effects similar to those of the Paraguay tea (see MATE), which is another species of iler, being at first exhilarating if taken in moderate quantities, but in excess acting powerfully as an emetic,

was drunk by the men only; its first effects were those of a stimulant, but as the quantity taken was increased, one after another yielded to its emetic powers, and the ability to resist these the longest was regarded as an indication of superiority. Excessive vomiting was considered necessary to a proper purification for their ceremonials, and the drinking was continued until the tea was rejected unchanged in appearance. On account of its emetic properties the shrub has been called I. vomitoria, which name, however descriptive, cannot supersede the older I. cassine. In North Carolina, according to Barton ("Collections"), the people make use of it to purify and improve brackish water, a few leaves being boiled in it for a short time. Where the plant grows naturally its leaves are used as a domestic medicine, to act as a diuretic, emetic, or purgative, according to the quantity administered. They are also used in moderate quantities as a substitute for ordinary tea.

YAVAPAI, the N. E. county of Arizona, bounded N. by Utah and E. by New Mexico; area, over 50,000 sq. m.; pop. in 1870, 2,142. The Colorado river crosses the N. W. corner, passing through deep and precipitous cañons. The N. E. corner is watered by a tributary of the Rio San Juan, the S. part by several affluents of the Gila, and the S. W. corner by the Rio Santa Maria, a branch of Bill Williams fork. The Colorado Chiquito, for a considerable portion of its course walled in by precipitous cañons, flows N. W. through the county near the centre, and empties into the Colorado. The greater portion of the surface has an elevation of 5,000 or 6,000 ft. above the sea, and some parts rise much higher. There are nu

and returns, or (what is the same thing) starting from the equator at the vernal equinox of our hemisphere performs its complete circuit to the vernal equinox again, is termed the tropical year; but it will be convenient, and is more instructive, to define the year in general terms as the period in which the earth completes the circuit of her orbit around the sun. Like all such intervals, the year varies in length according to the way in which it is measured. If we consider the earth's path without reference either to its shape or to the

YAZOO, a W. county of Mississippi, bounded S. E. by Big Black river, and intersected by the Yazoo; area, 650 sq. m.; pop. in 1870, 17,279, of whom 12,395 were colored. The surface is level, and the soil a rich alluvium. The Mississippi Central railroad passes along the E. extremity. The chief productions in 1870 were 290,448 bushels of Indian corn, 5,171 of Irish and 35,509 of sweet potatoes, and 26,047 bales of cotton. There were 1,938 horses, 2,775 mules and asses, 3,040 milch cows, 7,563 other cattle, 1,838 sheep, and 11,251 swine. Capital, Yazoo City.

YEAMES, William Frederick, an English painter, born in Taganrog, Russia, where his father was British consul, in 1835. He studied in London, and spent several years in Florence, returning to England in 1858. In 1866 he became an associate of the royal academy. His works, consisting of historical and genre pictures and landscapes, include "The Toilet," "The Rescue,' 66 Lady Jane Grey resisting Feckenham's Efforts to convert her," "The Fugitive Jacobite," "Sir Thomas More taken to the Tower," "The Infirm Child near the Fireside," "The Young Knight Arming," "Monks Scourging Themselves," and "Reception of the French Ambassadors by Queen Elizabeth after the St. Bartholomew Massacre." YEAR, a period of time well known within and near the temperate zones of the earth as that in which the four seasons run through their course, and indicated upon all parts of the earth's surface by the apparent return of the sun at midday to the same position in the heavens, as from its place at our summer or winter solstice forth and back to the same place again, the length of which period corresponds nearly to the time of 3651 diurnal revolutions of the earth (i. e., days). For the astronomical principles that determine or explain many of the points in relation to the year, see ASTRONOMY, SUN, MOON, PRECESSION OF THE EQUINOXES, and NUTATION.-The year, as just defined, or that in which the sun, from having its place over either tropic, moves to the other

to the sun as centre and to the surrounding star sphere. Supposing a line drawn always to the earth's centre from the sun and prolonged to the star sphere, this line would travel round like the hand of a mighty dial; and the time in which it would complete one circuit is called the sidereal year. This period may therefore be defined as the interval between the successive returns of the earth to the same heliocentric position among the fixed stars, or the period in which the earth viewed from the sun's centre would appear to complete the cir cuit of the ecliptic. The sidereal year is not absolutely constant, because the earth is ex posed to the perturbing influence of the other planets. Its mean value is 365d. 6h. 9m. 9'68, Whether, apart from perturbations, the sidereal year is undergoing a secular change of length, is a question as yet undecided; certainly any such change must be exceedingly minute. But instead of referring the earth's motion to the star sphere, we may consider it with reference to the shape of the earth's orbit. This orbit has two axes, for example, and either extremity of either axis might be considered as a starting point from which the year might be measured; so that we might measure a year as the interval between successive passages of the perihelion, or of the aphelion, or of mean distance following perihelion, or of mean distance following aphelion. Any one of these periods might be called the anomalistic year, because its beginning would be counted from the time when the anomaly either vanished or had its maximum value. In practice, however, the term is limited to the year mea sured from the perihelion. Thus the anomalistic year is the interval separating successive passages by the earth of the perihelion of her orbit. As the perihelion advances, the earth, after completing a circuit from perihelion to the same heliocentric longitude, has still to pass over the arc by which perihelion has advanced in the interval. Accordingly the anomalistic year exceeds the sidereal year; its mean length at present is 365d. 6h. 13m. 48-6s. It may perhaps appear strange to have the mean length at present spoken of, instead of the ab solute mean; but the motion of the perihelion is so irregular, and passes through so many varying conditions in the course of long intervals of time, that we must be content to consider its present general rate of advance. It

may be added that the interval between successive passages of the perihelion is not, as might be supposed, equal in length to the interval between successive passages of the aphelion. This is easily shown. The perihelion is at present advancing at the rate of 11.24" per annum; so that, neglecting the minute gain while the earth is traversing this arc, the actual anomalistic year, estimated from the perihelion, exceeds the sidereal year by the time occupied by the earth in traversing an arc of 11.24" with her perihelion motion of 1° 1' 9.9" per diem. Now if the anomalistic year were estimated from aphelion, the same would be true, only the earth's daily aphelion motion of only 57' 11.5" must be substituted. Since, with the more rapid motion, the arc 11.24" would be traversed in less time, the anomalistic year estimated from the perihelion is slightly shorter than the anomalistic year estimated from aphelion. The length of the mean anomalistic year, however, is at present that above indicated, and therefore it follows that at present the actual interval between the earth's successive passages of perihelion is slightly shorter than the mean anomalistic year. Thirdly, the year may be measured with reference to the earth's figure and position. For example, the plane of the earth's equator cuts the plane of the ecliptic in a straight line, which is carried round with the earth, moving almost exactly parallel to itself. Twice in each circuit, therefore, this line passes through the sun's centre, and the year may be measured from one or other of these epochs. One corresponds to the vernal equinox, the other to the autumnal equinox. Astronomers have selected the former to measure from, and the year thus measured is called the tropical year, or year of seasons, and is defined as the interval between the earth's successive passages of her vernal equinox. Since this point (when the earth viewed from the sun is at and the sun viewed from the earth is at ) retrogrades, the tropical year is less than the sidereal year. Its mean length is 365d. 5h. 48m. 48.6s. As in the case of the anomalistic year, the actual length of the tropical year depends on the point from which it is measured; for the earth's diurnal motion at the passage of her vernal equinox is not precisely equal to her motion at the passage of her autumnal equinox. Thus the length of the tropical year is not absolutely constant. Its length at present exceeds by nearly 13 sec. the length which it had in the time of Hipparchus. In like manner the length of the anomalistic year is slowly variable. The lengths of the four seasons, astronomically measured, are very nearly as follows: from the vernal equinox to the summer solstice, 92d. 22 h.; from the latter to the autumnal equinox, 93d. 134h.; from this to the winter solstice, 89d. 16 h.; from this to the vernal equinox, 89d. 14h.-For an account of the years and calendars of different nations, see CALENDAR, and CHRONOLOGY.

YEAST, the froth which rises upon the surface of beer and other liquors during fermentation, consisting principally of microscopic globules of a fungoid plant. This plant is also found in that variety of yeast which is developed in sedimentary fermentation. (See BREWING.) The history of this plant begins with its discovery in beer by Leeuwenhoek in 1680 by microscopical examination. Fabroni in 1787 regarded yeast as a vegeto-animal substance residing in peculiar utricles in grapes as well as in corn, but does not seem to have attached great importance to the existence of the yeast globules discovered by Leeuwenhoek. Thénard in 1803 recognized a relation between yeast cells and fermentation, but most of the chemists of that day who investigated the subject of fermentation seem to have regarded the functions of yeast as having more of a chemical than a physiological nature. In 1825 Desmazières found organisms in yeast which he regarded as animals. It was not till about 1837 that Cagniard de la Tour took up the microscopical observations of Leeuwenhoek, and, as has been said, "rediscovered the yeast plant." He declared that by its influence the equilibrium of the molecules of sugar was broken up, and measured the diameter of the cells, which he placed at of an inch, and also observed that they developed by budding. Schwann of Jena made independently, about the same time, similar discoveries. Their observations were confirmed by Quevenne, Mitscherlich, and Turpin; the last placed the organism in the genus torula of Persoon, and this classification has been recognized until very recently. Yeast has also received the name of mycoderma vini. The torula has a mycelium, and it is held that ferments never have. Meyen, considering yeast to be a fungus, created a new genus for it under the name of saccharomyces. Kützing and others placed it among algæ, and in a separate genus called cryptococcus. Whether yeast is the cause or the effect, or simply an accompaniment of fermentation, has long been disputed, and it has not been positively decided that its presence is necessary for the commencement of the process of vinous fermentation; but the great weight of opinion leans toward the affirmative. (See FERMENTATION.) The most prominent advocate of this theory is Pasteur, who has made numerous elaborate experiments, not only to elucidate the nature of yeast, but to oppose the theory of spontaneous generation. Reess and others have divided the yeast genus of fungi into several species. Of these, saccharomyces cerevisia, or the yeast of beer, is again divided into two varieties, sedimentary or bottom and surface yeast; but the drawings of them have much resemblance, and in fact it is known that the one variety is readily convertible into the other by cultivation. The sedimentary yeast is developed at a considerably lower temperature than surface yeast, and with much less evo

its activity can be readily restored by raising the temperature of the fermenting mass, in which case, after a few fermentations, the sedimentary is converted into surface yeast. The cells of saccharomyces cerevisia are round or oval and from 00031 to 00035 of an inch in diameter. (See figs. 1 and 2.) The cell wall is an elastic membrane of colorless cellulose, with colorless protoplasm, which often contains small granules, and one or two vacuoles containing cellular juice. When the cells are not undergoing development they are usually separate; but when the yeast is forming, its method of growth causes the cells to be joined to one another in pairs, groups, or chains, the latter being more particularly the case in the rapid development of surface yeast. During fermentation, or the development of yeast, there is an elevation of temperature, probably due to the combustion of oxygen, which may be obtained from the air or from the decomposition of sugar in the fermentable liquid. In fact the respiration or consumption of oxygen by the yeast cells bears some comparison to the respiration of animal pulmonary tissue. The multiplication of the cells of saccharomyces when in contact with an appropriate fermentable liquid is by budding, but under other cir

is Pasteur's ordinary alcoholic ferment of wine. The adult cells have an ellipsoidal form, being about 00024 in. in length by 000176 in. in breadth. (See fig. 3.) The multiplication by budding and by spores does not differ from that of S. cerevisia. S. exiguus, fig. 4, according to Reess, has cells of only 000098 in. in breadth by 000118 in. in length, and multiplies like the other varieties. S. con glomeratus, fig. 5, is rare, and is found mostly in the must of wine toward the end of fermentation. It has spheroidal cells ⚫000236 in. in diameter, conglomerated together; the cells, springing from buds, do not become detached from the parent cell until they have attained the same size. S. apiculatus, fig. 6,

is the most abundant alcoholic ferment, and is found on the surface of all kinds of fruit, especially on berries and stone fruits. It has been found in certain kinds of beer, as that of Belgium, which undergoes spontaneous fermentation, yeast not being added to the wort. According to Engel, this species does not belong to the genus saccharomyces, and he calls it carpozyma apiculata. The greater diameter of the cells is about 000236 in. S. Pastorianus, fig. 7, is a species which appears in the

torianus, alcoholic ferment sii, ferment of red wine, of wine, magnified 400 diam- magnified 350 diameters. eters.

after fermentation of wines, especially of sweet wines, and those of other fruits than the grape. The cells are oval, pyriform, or clubshaped, and vary in dimensions from 000236 to 00078 of an inch. S. Reesii, fig. 8, accompanies S. ellipsoideus in the must of red wines. It has elongated cylindrical cells. S. mycoderma (mycoderma vini) is shown in fig. 9. The mucor mucedo and M. racemosus, fig. 10, have the property, when placed in a solution of sugar and protected from access of oxygen, of transforming or dividing their mycelium into joints having the form of balls, which latter multiply by budding. "This fact," Schüt