Page:The American Cyclopædia (1879) Volume XVI.djvu/802

 774 YAZOO YEAR merous mountain ranges, generally running N. and S. The N. part is mostly unexplored. The central and E. portions contain valuable farming, pastoral, and mining lands. -The set- tlements are in the southwest, in the mining regions of Prescott and Wickenburg. The soil here is fertile, and pine forests abound. Gold and silver are found. In the northeast are the Moqui Indians. Capital, Prescott. YAZOO, a river of Mississippi, formed by the junction of the Tallahatchie and Yalobusha rivers at Greenwood in Leflore co. From the junction it pursues a serpentine course, gener- ally bearing S. W., till it enters the Mississip- pi above Vicksburg. Its length is 240 m. It is very narrow, deep, and sluggish, flowing through a rich alluvial country, and is naviga- ble throughout. The Tallahatchie is navigable by steamers in high stages of water to Panola, and the Yalobusha to Grenada. 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. lie studied in London, and spent several years in Florence, returning to England in 1858. In 1866 he be- came 'an associate of the royal academy. His works, consisting of historical and genre pic- tures and landscapes, include "The Toilet," "The Rescue," "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 " Recep- tion 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 corre- sponds nearly to the time of 365J diurnal revo- lutions of the earth (i. ., days). For the as- tronomical principles that determine or explain many of the points in relation to the year, see ASTRONOMY, SUN, MOON, PRECESSION OP 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 and returns, or (what is the same thing) start- ing 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 com- pletes 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 earth's own figure, we must refer her motions 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 pro- longed to the star sphere, this lino 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. 9'6s. Whether, apart from perturbations, the side- real year is undergoing a secular change of length, is a question as yet undecided; cer- tainly 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 con- sidered as a starting point from which the year might be measured; so that we might measure a year as the interval between successive pas- sages 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 bo called the anomalis- tic year, because its beginning would be counted from the time when the anomaly either van- ished or had its maximum value. In practice, however, the term is limited to the year mea- sured from the perihelion. Thus the anomalis- tic year is the interval separating successive passages by the eartli 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 ad- vanced in the interval. Accordingly the anom- alistic year exceeds the sidereal year ; its mean length at present is 365d. 6b. 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 inter- vals of time, that we must be content to con- sider its present general rate of advance. It