ical method for measuring small distances and for producing small displacements.
Ordinary screws are generally made by forcing a steel nut, called a die, over a cylinder of metal. In like manner, nuts are made by forcing a conical screw, provided with sharp cutting-edges, through a hollow cylinder of metal. This conical screw is called a tap. Higher grades of screws are made by placing a cylinder between the centers of a lathe and then moving the cutting tool along the lathe-bed on a carriage which is itself operated by another screw.
With elaborate precautions, Professor Rowland (q. v.) succeeded in this way in making a more perfect screw than had ever been made before, on which, when finally corrected, moved the ruling-point of a dividing-engine with such accuracy that no single ruling was in error by as much as 1-100,000 of an inch. Woodscrews, so-called, are metal cones, upon which a thread has been cut and a slotted head made. They have pointed ends for starting into wood, where they cut their own nuts and act rather as clamps than screws. Consult Screw, in Encyclopædia Britannica, by Rowland and Rankine's Machinery and Millwork.
Screw-Propel′ler, a wheel with two or more radial blades in the form of a helix or spiral, used to propel a vessel. In modern ocean-steamers, there generally are two propellers, one on each side of the keel. The action of the propeller is similar to that of a screw revolving in a fixed nut, the water being more or less fixed as regards the revolving propeller. The screw-propeller was suggested by Bernouille of France in 1752, and in 1801 John Stevens of Hoboken, N. J., made a successful experimental boat with a screw-propeller. But it was not until between 1835 and 1840 that it began to come into general use. Its practical use was then demonstrated by F. P. Smith in England and by Capt. John Ericsson, first in England and later in the United States. Ericsson is generally given the credit of having made the first successful application of the screw-propeller to steam-navigation. At present it is the only method of propulsion used on large steam-vessels. The design of the shape and size of the propeller depends on conditions more or less peculiar to each vessel, and requires not only calculations but often experiments before the best shape is found for a given boat. Propellers are generally made of gun-metal. The dimensions of the propellers and shafts on the transatlantic steamers are very large. For the Celtic, a White Star steamer of 14,259 tons displacement, the two propellers each have a diameter of 20 feet and are carried on steel shafts of 19½ inches diameter. Consult the U. S. Navy Dept.'s professional papers.
Scribe, a name used among the Jews originally to indicate a military officer, whose business was recruiting soldiers and levying taxes. Later the name was given to those who copied the books of the law, and, as those who copied the law became its best expounders, the word had in the time of Christ come to mean an expounder of the law or a learned man. Scribes were found all over Palestine, and were reverenced by the people as public teachers and lawyers. Some were members of the Sanhedrin or court, and some had public class-rooms, where their disciples sat at their feet. Those who did not fill these higher places were engaged in copying the books of the law and of the prophets and in writing contracts, letters of divorce etc. See Schürer's History of the Jewish People in the Time of Christ.
Scud′der, Horace Elisha, American man-of-letters, was born at Boston, Mass., Oct. 16, 1838, and graduated at Williams College. After teaching for three years in New York City, he took to writing stories for youth and edited a magazine in their interest. From 1890 to 1898 he edited The Atlantic Monthly, and became a resident of Cambridge, Mass. Here he assiduously pursued a literary life, writing, besides his successful series of The Bodley Books and a brief History of the United States, a monograph on Noah Webster, an historical biography of Washington and a collection of essays and criticisms entitled Men and Letters. He was the editor, also, of the series of volumes of the American Commonwealths and author, jointly with Mrs. Taylor, of the Life of Bayard Taylor. He was one of the writers, moreover, of Bryant and Gay's History of the United States and of Justin Winsor's Memorial History of Boston. Above all, he wrote the classic biography of James Russell Lowell. He died on Jan. 11, 1902,
Sculpture (skŭlp'tū̇r), from a Latin word meaning to cut out or carve, is the art of representing the form of an object in a solid substance. When a figure is only partly raised from a background, it is called relief and has different names according to the degree in which it is raised, as bas-relief, meaning low relief. Wood, marble, granite, bronze, gold and ivory are some of the materials used in sculpture, anything that can be cut or molded into shape being used. The Greeks and Romans worked largely in marble, especially the pure, white marble brought from Paros (q. v.) called Parian marble. The art is an ancient one, beginning with the use of memorial stones and the making of images of the gods. The Egyptians are among the earliest nations to use sculpture in their religion, their temples being covered with reliefs, while innumerable statues of gods stood upon their plains. The Sphinx was probably sculptured about 4,000 B. C. The specimens of Assyrian sculpture found
