CYCLXTS. 707 (London, 1894). See Eustpterus; Prest- wicniA : Xiruosi RA. CYDIPTE (Ck. KvdlTnrr,). The Athenian niaideii ciallily won by Acontius. l"or llie de- tails of the story, see Acoxriis. CYDTJUS (Lat., from Gl^. KMvof, Kydnos) . A river of Cilicia, passing the city of Tarsus and emptyini,' into the JNIediterranean. It was on this riwr that Cleopatra made her voyage to meet Antony. CYDO'NIA. See QuiJ^CE. CYGN^'US, Fredrik (1807-81). A Finnish poet ami liti'rary historian. He was born at Tawastehus, and was educated at the University of Abo, where he lectured from 1839 to 1843, in hich year he began an extensive tour through Europe. In 1854 he was called to the chair of a!sthetics and modern literature at the Uni- versity of Helsingfors. He bequeathed his entire fortune and his valuable art collection to the State. His poetic worl-cs were published by him under the title Skaldestyckcn (6 vols., 1851-70). CYGN.ffiUS, UNO (1810-88). A Finnish edu- cator, bom at Tawastehus. From 1837 to 1839 he was a pastor and instructor at Wiborg, from 1839 to 1846 spiritual director of the colony at Sitka, Alaska, and in 1801 was appointed chief inspector of the Finnish public-school system, which he thoroughly reorganized. In 18G3 he established the first normal school in Finland, and until 1809 was its director. He was the first to make manual work {slojd, sloyd) a part of regular public-school instruction. He published Forslag rorande folksUolcviisendet (1861). CYG'NTJS (Lat., from Gk. KvKms, Kyknos, the swan). A constellation in the Xorthern Hemisphere, between I.3 ra and Cassiopeia. Sev- eral stars in this constellation have received the particular attention of astronomei-s. See Stars. CYLINDER (OF. ciUndre, Ft. cylindre, from Lat. cyUndnis. from Gk. /n//Ui»rfpof, kylindros, roller, from KvyivSiiv, kylindein, KvAittv, kylichi, to roil). A surface generated by a line (the generatrix) which moves parallel to a fi.xed line and touches a given cui-ve (the directrix) is called a cylindrical surface. The space inclosed by a cylindrical surface is called a cylindrical space. The portion of a cylindrical space limited by two parallel planes cutting all the elements oif the cylindrical surface is called a cylinder. If the directrix is a circle, the cylinder is called a circular cylinder; if the directrix is an ellipse, the cylinder is called an elliptic cylinder, and J so on. If the elements (positions of the gen- eratrix) are perpen- dicular to the plane of the directrix, the cyl- inder is called a right cylinder, otherwise it is called oblique. If a rectangle be revolved about one of its sides, a cylinder of revolu- tion, or a right circu- lar cylinder, is formed. The plane tigures which form the ends of a cylinder are called its bases, and these are always congruent. The perpendicular distance between the bases A CVLISDEK OF REVOLUTION CYLLENE. is called the altitude. The lateral area of any cylinder, expressed in surface units, is the product of the number of linear units in the perimeter of a section perpendicular to the ele- ments (right section) and the number of linear units in an element.* The number of units of volume of a cylinder is equal to the product of the number of square units of the base and the luinibor of linear units in the altitude of the cylinder. A IllGHT CIRCULAR CYLINDER. AX OBLIQUE C"XINDEB. B,, Bo. lower and upper bases ; E, an element; R, aright a, the altitude. section. A cylindrical surface may be considered as a conical surface (see Cone) with the vertex at infinity. Hence, plane sections of the cylindrical space of a right circular cylinder lead to the so- called conic sections, in particular, to the ellipse. If V S volume, C = curved surface, B = base, A = total area of surfaces, a = altitude, )• S radius of the base (or of the inscribed sphere) and E. = the radius of the circumscribed sphere of a right circular cylinder, then V = 7rr-a, C = 27rra, A = 2Trr- + 2irra = 27rr (r -|- a), R = V " 4- - 4+'--= The volume of it - ^/ a^ + 4 r sector of a cylinder of arc 7i arc is given in radian measure, as n radians, the plane parallel to the IS— x,-a; if the If the cylindrical segment is Y — ■ — sinPJ, volume is - nr-a. axis cuts off a segment, the corresponding are cut from the base being k° , the volume of r-a f k ~2 VI8O r if k° = n radians, V=— ;- (" — sin n ) . CYLINDER - SNAKE. One of a family (Ilysiida') of small burrowing snakes alliedtothe Typhlopid.T and shield-snakes, and retaining vestiges of pelvis and hind limbs, the latter showing in claw-like spurs protruding lietwecn the scales on each side of the vent. The form is cylindrical, the scales small, polislied. and hardl.v larger on the belly than elsewhere, and the colors bright. The few species are scattered over the Malay Islands and Indo-China, where the com- mon 'red snake' {Cylindrophis riifiis) reaches a length of two and one-half feet, and occur in Cey- lon and South .America. A beautiful species (Ilnaid scytnle) in tropical Soutli America is one of those called 'coral-snake,' and is coral-red with black rings. On account of its beauty, perfectly harmless nature, and 'for cooling purposes,' this snake is said to be sometimes worn as a neck- lace by the native ladies. CYLLENE, sll-le'ne (Lat, from Gk. KuWiJi'i;, Kylh'in'). A mountain in northwest Arcadia,
