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LATERAN

1034

LATHROP

restoration of the court of justice to the native Guatemalans was the last act before his death, which occurred on July, 1*66. See

7"   *_f        1          TT     1                                                                        **

Life by Helps.

Lat'eran, styled the Mother and Head of all the Churches of the City and of the World, in Rome, and now the church of St. John, surpassing St. Peter's in dignity, became imperial property in 66 A. D., and was given to St. Sylvester by Emperor Constantine. It was originally dedicated to the Savior, but Lucius II, who rebuilt it in the i2th century, dedicated it to St. John. The Lateran palace was the residence of the popes until the i4th century, but now is the property of the Italian government. The Holy Staircase, supposed to be the stairs of Pilate's house at Jerusalem, stands on the piazza of the church.

La'tex, the milky fluid which exists in plants belonging to several large families, of which the milkweed, bloodroot and spurge are well-known examples. It occupies special receptacles in the form of even or irregular branched tubes, abundant in all parts, from which it exudes when the plant is wounded. It is a watery fluid, containing a great variety of substances, as gums, oils, sugars, starch, coloring matters, caoutchouc. The caoutchouc, when it exists in proper form and amount, may be separated from the latex and is the source of the rubber of commerce, which is derived from several tropical trees. (See INDIA-RUBBER.) It is not unlikely that the latex tubes offer a means of transferring foods from one part of the plant to another.

Lathe. The la the is the most com-mon and most useful machine tool used in the mechanic arts. Indeed,until recently it practically was the only machine-tool found in the machine shop. It consists essentially of a rotating shaft or spindle, to one end of which is attached the work or piece to be turned. A cutting tool is forced against the work as it rotates, and thus all sections of the work can be brought to the form of a circle, but the circles may vary in size along the axis.

The spindle usually carries at its end a wheel having a plane side, called the faceplate. To this face-plate the work may be attached by means of bolts or by means of a single screw, as in wood-turning. Otherwise the work may be held in a "chuck" attached to the spindle and having jaws which clamp the work and hold it securely. Another method of holding the work is to pivot it between two cones called centers on the axis of the spindle, one rotating or "live" and the other still or "dead." The work is driven in this case by means cf a clamp or "dog" pinching the work and projecting into a hole in the face-plate.

For light work the cutting tool may be held by hand and supported by a tool rest close to the work. For heavier work and for more accurate work the cutting tool must be held rigidly attached to the slide rest. The slide rest can be moved slowly and steadily by turning suitable cranks by hand, or the mechanism moving the slide rest may be connected to the spindle of the lathe. In this way the slide rest is given an automatic motion proportional to the speed of the spindle which makes possible the cutting of screw threads with great facility.

The power may be furnished by the foot through a treadle or by an engine or other motor, either directly or through belts and shafting. The speed is determined by the work, turning iron requiring slower speed than either brass or wood. Lathes are of all sizes, from the little machines used in watch factories to the powerful machine-lathes used in turning flywheels. In the ordinary

ENGINE LATHE   WITH   FITTINGS

lathe the cutting is performed in circles about the axis passing through the lathe centers. The lathe has been adapted to turning other than cylindrical objects, by causing the tool to move, this motion being controlled automatically by a model. By this means such irregular objects as an axe-handle or a gun-stock can be turned on the lathe. This invention was made by Thomas Blanch-ard of Philadelphia in 1816. The potter's wheel, used from the most remote times, is supposed to be the origin of the lathe. Crude forms of lathes have certainly been used from the very earliest times, but it is only since the invention and wide use of the steam engine that the lathe has reached its present developed form.

La'throp, George Parsons, an American writer and editor, was born at Honolulu, Aug. 25, 1851, and was educated in Germany. He was assistant editor of the Atlantic Monthly from 1875 to 1877 an(i °f "the Boston Courier from 1877 to 1879. He was the author of Rose and Roof tree; Afterglow; A Study of Hawthorne; An Echo of Passion;