PLANCHETTE. 89 PLANE. two persons with the necessary qualifications hav- ing their hands upon it lightly, it begins to move and write answers to questions sometimes of a puzzling character. These answers are asserted by believers in spiritualism to be communications from the spirit world. PLANCK, plank, K.rl Christian (1819-81). A German philosopher, born at Stuttgart, and educated in philosophy and theology in Tubingen. In 1844 he became tutor and librarian at the theological seminary there, and lecturer on phi- losophy at the university. From 1856 to 1809 he was professor at the gymnasium of Ulm, and in 1879 he became principal of the seminary in Maulbronn. Planck defends in his numerous writings the speculative system of philosophy as opposed to that of empiricism. His chief work is Die Weltalter (1850), in which he treats of the system of pure realism and subjective idealism. In his Anthropolotjie uniJ PsiicJiohir/ii' uuf nafiir- uAssenschfiftlichrr Griindlage (1874), he vigor- ously combats the theories of the atomists and materialists, and he takes his stand against Dar- winism in Wahiheit und Flachlieit des Danoin- ismics (1872). PLANQON, plaN'soN', Pol (I860-). A French basso, born in the Ardennes. He was sent to Paris by his parents and there, despite his own inclinations, entered a business house. Through the friendship of Theodor Eitter he was enabled to study music, and finally entered the Ecole Duprez and devoted himself entirely to music. In 1881 he made his debut in Les Hu- guenots at Lyons. Two years later he ap- peared at the Paris Grande Opera as Mephisto in Faust, in which role, as well as that of Ramfis in Verdi's A'ida, his success was pro- nounced. He created the roles in Saint-Saens'a Ascanion. in Massenet's Le Cid, and in Gounod's Sapho, upon its revival in 1893. He appeared for a number of seasons at the Metropolitan Opera House in New York, where he was a prime favorite. PLAN'CXJS, Lucius MuNATius. A Roman politician and soldier. He was born at Tibnr, near Rome. In youth he was one of Cicero's pupils in oratory, and later was an officer of Csesar in the Gallic wars. After the assassina- tion of Ciesar, Plancus at first favored Brutus, but soon went over with four legions to Antonius. In B.C. 42 he w'as consul with Lepidus. In the contest between Antonius and Octavianus he sided with the latter, and proposed in the Senate to confer upon him the title of Augustus. Plan- cus was a man of some literary taste, and to him one of Horace's odes is addressed. PLANE (Lat. phinum. level ground, plain, neu. sg. of jilnmiK, level, flat, plane, plain). A surface which is determined by any three of its points not in a straight line. A plane surface is said to have zero curvature. When two planes intersect, their intersection is a straight line. The inclination of one plane to another, or the dihedral angle (see AnfiLE) between the planes, is measured by the plane angle whose arms lie in the respective planes and are perpendicular to their intersection. When this angle is a right angle, the planes are perpendicular to each other. As a result of the definition, a plane is deter- mined by a straight line and a point not in that line, or by two intersecting lines or by two par- allels. A group of several planes having a com- mon line of intersection is called an a.xia! pencil. Several planes having a conmion point of inter- section are called a sheaf of planes. Plane Figures. Any combination of co- planar points and lines is called a plane figure. See Polygon. PLANE (OF., Fr. plane, from Lat. plaUiiiiis, f.rom Gk. TXiravos, plane tree, from ttXoti/s, phili/s, flat, Lith. platus, Skt. prthu, broad, from piiith, to spread out; so called from the broad, flat leaves), Platanus. The only genus of the nat- ural order Platanaeeje, tall, large trees of which there are only four or five species. The flowers are in globose, small, pendulous, long-stalked cat- kins, which give the tree a peculiar appearance in winter. The species of plane are natives of temperate climates in the Northern Hemisphere; have deciduous large palmate leaves, and smooth whitish bark, which annually scales ofT in large pieces. The Oriental plane (Pl-atanns orientalis) , a native of Greece and the East, early used by the Greeks and the Romans as an ornamental tree, is extensively planted for shade and orna- ment in various regions. Few trees better endure the atmosphere of large cities. A tree is reported on the banks of the Bosporus, which is 141 feet in circumference at the base, extends its branches 45 feet from the trunk, and is believed to be more than 2000 years old. The wood of the plane, when young, is yellowish-white: when old, it is brownish, fine-grained, takes a high polisli, and is esteemed for cabinet-making. The tree thrives best in a rich alluvial soil in the vicinity of water. The North American plane, sycamore, or buttonwood (Platanus occidentalis) , is very PLANE I'KEE OR BUTTONWOOD. similar and is probably the largest deciduous tree of the United States. It abounds on the banks of the great rivers of the Middle States, where it attains a height of 100 to 150 feet and 10-15 feet in diameter. Its timber is not very valuable, and is very liable to decay. Two other species occur in the Southwest, the Californian sycamore (Platanus raccmosa) and the Arizona sycamore (Platanus Wrlghtii) . The name plane tree is commonly given in Scotland to the syca- more or great maple (Acer pseudo-platanus), which resembles the nlane tree in its foliage. Sec Maple. PLANE (Fr. plane, from !ML. plana, plane, from Lat. planare, to plane, level, from planus.
