406 



CONDURANGO 



CONE-SHELL 



the metallic support, the metal is termed a con- 

 ductor of electricity ; in the latter, the glass or 

 ebonite is termed a non-conductor or insulator, 

 since by its means the charge is prevented from 

 leaving the body. This distinction is somewhat 

 artificial, since no substance is known to be either 

 a perfect conductor or an absolute insulator. The 

 substances in frequent use as conductors and non- 

 conductors may be arranged in the following order 

 of their conductivity, beginning with the best : 

 Silver, copper, gold, brass, /inc, platinum, iron, 

 tin, lead, mercury, German-silver, graphite, red 

 phosphorus, mineral acids, saline solutions, sea- 

 water, pure water, alcohol, wood, ice, vegetable 

 oils, lime, chalk, camphor, porcelain, wool, hair, 

 silk, glass, wax, sulphur, resin, amber, gutta-percha, 

 shellac, paraffin, ebonite, air and other gases. 



It is found that the efficiency of a non-conductor, 

 when used as an insulator in electrostatic experi- 

 ments, depends very largely on the state or its 

 surface. In a damp atmosphere, glass becomes 

 coated with a thin film of moisture which consider- 

 ably lessens its insulating power. Hence these 

 experiments succeed better in dry weather ; other- 

 wise the apparatus requires to be heated, or the 

 glass insulators employed to be coated with shellac 

 varnish, upon which, moisture does not so readily 

 deposit. In metals, conducting power decreases 

 when the temperature is raised ; on the other 

 hand, glass, wax, sulphur, and some other 

 bodies which are extremely bad conductors at 

 ordinary temperatures, conduct very much better 

 when raised to a sufficiently high temperature. 

 It has been observed that a series 01 metals 

 arranged in order of their electrical conducting 

 powers, exhibits the same order as when similarly 

 arranged for their thermal conducting powers ; in 

 other words, metals which conduct electricity well, 

 conduct heat well. Also, that when two specimens 

 of the same metal differ in electric conductivity, 

 they differ in thermal conductivity, and in the same 

 way. See LIGHTNING CONDUCTOR. 



CondlirangO is the name of several South 

 American Aselepiadaceae (q.v. ), whose bark affords 

 a drug used as a remedy for venomous bites. 



Condyle, a protuberance on the end of a 

 bone, serving for articulation with another bone ; 

 especially that by which the occipital bone of the 

 skull is articulated to the spine. 

 Condy's Fluid. See MANGANESE. 

 Cone. In general, the term cone is applied to 

 any surface described by the motion of a straight 

 line which always passes through a fixed point and 

 G also intersects some 



curve in space. But 

 more particularly, 

 the word is used to 

 denote a right cir- 

 cular cone i.e. the 

 solid produced by 

 the revolution of a 

 right-angled triangle 

 round one of the 

 sides containing the 

 right angle. Thus 

 (see fig.), let ODC 

 be a triangle with a 

 right angle at D ; if 

 it revolve round 

 OD, then in moving 

 through successive 

 positions, OC will 

 trace out the cone, 

 OABC. The point, 

 O, is termed the vertex; the height, OD, the 

 altitude; the line, OD, the axis ; and the circle, 

 ABC, the base of the cone. The line, OC, by whose 



motion the cone is produced, is termed a generating 

 line, or generator. In the oblique cone, the axis is 

 inclined to the base at an angle other than a right 

 angle. A truncated cone is the lower part of a cone 

 cut by a plane parallel to the base. 



The lateral surface of a right circular cone is 

 obtained by multiplying half the circumference of 

 the base into the slant height of the cone ; the solid 

 content, or volume, is equal to one-third of the area 

 of the base multiplied by the altitude. 



In considering the different possible sections of a 

 cone by a plane, it is necessary to remember (as 

 is indicated in the figure) that a cone is really pro- 

 duced in duplicate ; that the generators, after 

 passing through the fixed point, O, form another 

 cone, such as OEGF. Different positions of the 

 sectional plane produce different curves, according 

 as it is parallel to the base, a generator, the axis, or 

 parallel to none of these ; so, consequently, we have 

 a circle, parabola, hyperbola or ellipse, respectively. 

 See articles CIRCLE, ELLIPSE, HYPERBOLA, PA- 

 RABOLA. 



Cone is a term used in Botany, with consider- 

 able latitude and variety of application. The 

 growing point or bud of any ordinary higher plant 

 is of more or less acutely conical shape, and the 

 young leaves at first arise in close succession upon 

 it. But while in vegetative growth the axis 

 usually lengthens and the leaves develop and 

 expand, the onset of reproductive functions may 

 check these changes. In the simplest cases the 

 leaves may become partially modified for pollen or 

 ovule bearing, as stamens or carpels, while the leaf 

 apices do not wholly lose their leafy character and 

 arrangement ; thus we have the cone-like male and 

 female flowers of Cycads (q.v.). In the allied 

 conifers, which include the most characteristic cone- 

 bearing trees, the leafy character of the crowded 

 stamens composing the male flower may be almost 

 entirely lost ; but in the female the structure of the 

 familiar cones (e.g. Scotch fir, spruce, larch) has 

 been the subject of enormous controversy ; since 

 from one point of view it is regarded as a single 

 flower composed of many carpellary leaves (each 

 bearing a biovular placenta on its upper surface ); 

 while from the other it must be viewed as an in- 

 florescence of which the crowded bracts bear axil- 

 lary biovular branches (see GYMNOSPERMS). The 

 cones of Coniferse may vary greatly from their 

 typical shape, witness the almost spheroidal cones 

 of Araucarias, while the number and crowded suc- 

 cession of the leaves in ordinary cones may be much 

 reduced and simplified e.g. cypress. 



The apparent cones which occur in some orders 

 of dicotyledonous plants are always due to a 

 crowding of the inflorescence. Thus, the so-called 

 cone of Casuarina (q.v.) is simply produced by the 

 crowding of the fruit ; that of Hop or Gale ( q. v. ) 

 by the overlapping of the leafy bracts which conceal 

 the small reduced flowers. But the term is with 

 advantage disused by most botanists outside the 

 limits of the Gymnosperms. 



Coneglia'no, a picturesque town of Northern 

 Italy, 31 miles NE. of Venice by rail. It was the 

 birthplace about 1460 of the painter Giambattista 

 Cima, called often Conegliano. Pop. 4682. 

 Cone-Shell (Conidce], a family of Gasteropod 

 molluscs, with substantial conical shells. The last 

 whorl of the spiral is much larger than those which 

 precede it and simply form the apex of the cone. 

 The aperture is long and narrow, with a sharp- 

 edged outer lip. The head of the animal has a 

 long proboscis ; the ' foot ' is long and narrow as 

 the aperture suggests ; the respiratory siphon is 

 short and thick. In the living state the shell is 

 covered by a yellowish epidermis, and it is only 

 when this is rubbed off that the great beauty 



