no little conflict, contending for possession of feeding-ground for flock or herd. Sheep-shearing is done both by hand and by machinery. Expert shearers in the west travel from place to place, beginning in the south and working their way north.
Sheeps′head, a bony fish common along the Atlantic coast and regarded as one of our best food-fishes. They are distinguished by wide cutting-teeth in the front of their jaws and by grinding-teeth behind. Their food is hard-shelled animals, young oysters, other mollusks, barnacles and the like. They vary in size from two pounds in the south to fifteen in the north, but the average size is about seven pounds, They range from Cape Cod to Texas. The fresh water drum and some other fishes are locally called sheepshead.
Shef′field, a manufacturing city of England, is situated in Yorkshire, where the Sheaf and Don Rivers unite, 38 miles south of Leeds. The town is well-built, over $2,000,000 having been spent in street improvements in 1878. The Church of St. Peter, built in the reign of Henry I; St. Mary's, with a fine spire; Albert Hall; Norfolk Market, built by the duke of Norfolk at a cost of $200,000; Music-Hall; and the new town-hall with a statue of Vulcan are among the noticeable buildings. Wesley College, Firth College, Mechanics' Institute, Athenæum, St. George's Museum, founded by Ruskin, and Mappin Art Gallery are some of its institutions. Sheffield has long been noted for its cutlery, the "Sheffield whittle or knife," being spoken of by Chaucer. The Cutlers' Company was founded in 1624, and the cutlers' annual feast dates from that time. The manufactures include brass, iron and steel articles of every kind and armor-plates, railroad-springs, tires and rails.
Sheffield from the Saxon times was the capital of a district belonging to a Norman family named Lovetot, who built a hospital, a mill and a bridge over the Don. It passed by marriage to the Furnivals, and suffered in the Wars of the Barons, the castle being burned and many of the people slaughtered. During the Wars of the Roses the Shrewsbury family, the ruling family of the county, sided with the House of Lancaster. The castle of the earls of Shrewsbury was a fortified building covering four acres of ground, and here Queen Mary of Scotland was imprisoned for 14 years. In 1644 the castle was taken by the army of Parliament, and soon after torn down. In 1864 a reservoir gave way, with terrible effect; 250 lives were lost and millions of property destroyed. Population 478,763. See Gatty's Sheffield, Past and Present, and Leader's Reminiscences of Old Sheffield.
Shel′byville, Ind., a city, seat of Shelby County, on Blue River and on the Clev., Cin., Chic, and St. Louis and Pittsburg,
Cin., Chic, and St. Louis railways, 26 miles southeast of Indianapolis, Besides the city-hall, court-house and Carnegie Public Library, it has attractive buildings, including good schools and churches. It is in a good agricultural region, and ships (besides farm-products) live-stock, flour and grain. It has a varied and increasing number of industrial establishments and a rapidly extending trade. Population 10,041.
Shel′drake, a large Old-World, saltwater duck of peculiar breeding-habits. The common European sheldrake is about the size of a mallard and brilliant of plumage. The head and neck are green with a white collar, and a broad chestnut band below this, over the chest and back. The shoulders and middle of the under parts are black, the wing-spot is green, and the bill and its knob are bright carmine. These birds breed in sand-dunes, in chambers made by themselves or by rabbits. Nest-chambers, two or three feet deep, are made in a grassy hillock. Each nest-chamber is covered by a moveable lid of sod. The nest-chambers are clustered and connected by galleries provided with a common entrance. Sometimes ten or 20 nest-chambers will be found in one group. Inhabitants of the sandy islands off the western coast of Jutland plunder these nests by removing the lid. All eggs above six in number are taken, and also the soft down with which the nests are lined. The sheldrakes of the United States are mergansers or fish-ducks, and belong to a distinct group.
Shell, the hard covering of an animal or an egg. While shells exist in great variety, those of the mollusks are the most typical—for example, those of the common snail and the common clam. These shells are secreted by gland-cells in the outer covering of the animal. The outside of a clam shell is a horny layer, differing materially from the inside, which always is pearly. There also is a middle layer, forming a large part of the shell and composed of regular prisms. The clam-shell therefore has three distinct layers—outer, middle and inner. The inner pearly layer is secreted by cells in the general surface of the mantle, while both the outer and middle layers are formed by cells in the thickened margin of the mantle. The substance of the shell largely is carbonate of lime, but the outer layer is horny rather than limy. The immense variety of sea-shells are formed in a similar way, and the shells afford a means of identifying the animals that formed them. The shell or test of the sea-urchin is made of six-sided plates of carbonate of lime, secreted by the cells of the outer covering of the body. The shell of the lobster and the crayfish, although formed by a similar process, is, nevertheless, made of a horny substance called chitin. This is also the
