Pl. vertices; also vertexes. [a. L. vertex whirl, whirlpool, VORTEX; crown of the head, highest point, summit, etc., f. vertĕre to turn. Cf. VERTICE.]
1. Geom. The point opposite to the base of a (plane or solid) figure; the point in a curve or surface at which the axis meets it; an angular point, as of a triangle or polygon.
1570. Dee, Math. Pref., C ij. From the vertex, to the Circumference of the base of the Cone.
1571. Digges, Pantom., IV. xxv. Hh ij. A transfigured Icosaedron may be resolued into 12 Pentagonal and 20 hexagonal Pyramides, concurring with their toppes or vertices all in the centers of this transformed body.
a. 1608. Dee, Relat. Spir., I. (1659), 355. 4 Triangles or rather Cones, of water, whose vertices rest cut off (as it were) by the middle stream of water.
1672. Boyle, Virtues Gems, 12. So as to make six triangles, that terminated like those of a Pyramid in a Vertex.
1715. Desaguliers, Fires Impr., 13. Two half Parabolas’s whose Vertex’s are C c.
1743. Emerson, Fluxions, 150. In the vertices of Curves, where they cut the Abscissa at right angles.
1840. Lardner, Geom., ii. 17. These lines are called the sides of the angle, and the point C where the sides unite, is called its vertex.
1860. Tyndall, Glac., I. vii. 54. Along the two sides of a triangle, the vertex of which was near the centre of the glacier.
1882. Minchin, Unipl. Kinemat., 12. The parallelogram must now be jointed at its four vertices.
b. Optics. (See quots.)
1704. J. Harris, Lex. Techn., I. Vertex of a Glass (in Opticks) is the same with its Pole.
1797. Encycl. Brit. (ed. 3), XIII. 288. Draw the ray RC through the centre, cutting the [spherical] surface in the point V, which we shall denominate the vertex, while RC is called the axis.
1803. Imison, Sci. & Art, I. 348. To find the vertex or centre of a lens.
1867. J. Hogg, Microsc., I. ii. 18. The point where the axis cuts the surface is called the vertex of the lens.
c. Astr. (See quot.)
1876. G. F. Chambers, Astron., 922. Vertex..., a term used to designate that point in the limb of the Sun, the Moon, or of a planet, intersected by a circle passing through the zenith and the centre of the body.
2. The point in the heavens vertically overhead, or directly above a given place; the zenith. Latitude or meridian of vertex (see quot. c. 1850).
1646. Sir T. Browne, Pseud. Ep., II. ii. 62. The true meridian is a major circle passing through the poles of the world, and the Zenith or Vertex of any place.
1665. Sir T. Herbert, Trav. (1677), 5. These sorts of people freeze within the polar circles,… the Pole being their vertex, and the Æquator … their direct Horizon. Ibid., 39. The heat … when the Sun comes to the Vertex, is much more intense … than it is about the Polar Circles.
1715. trans. Gregory’s Astron. (1726), I. 346. When the Phænomenon … is in XDZ the common Azimuth … of the two places on the Earth pitch’d upon for this purpose, whose Vertices are X and Z.
1748. Anson’s Voy., II. v. 182. The Sun was within about three degrees of the vertex.
c. 1850. Rudim. Navig. (Weale), 54. Either of these points is called the vertex of the great circle to which it belongs; the arc intercepted between the vertex and the equator is the latitude of vertex; the meridian that passes through the vertex is the meridian of vertex.
1867. Smyth, Sailor’s Word-bk., Vertex, the zenith, the point overhead.
3. Anat. (and Zool.). The crown or top of the head; esp. in man, the part lying between the occiput and the sinciput.
[1615. Crooke, Body of Man, VII. ii. (1631), 434. The middle part of the scalpe … is gibbous or round;… the Latins call it Vertex, because in that place the haires runne round in a ring as waters doe in a whirle-poole.]
1638. A. Read, Man. Anat., III. i. 389. Vertex, the crown, that which is betweene the former two, somewhat arched.
1680. S. Haworth, Disc. Conc. Man, 115. The middle Part between these which is Gibbose is called Vertex.
1754–64. Smellie, Midwif., I. 86. [In child-birth] the crown or vertex is the first part that is pressed down, because … the bones at that part of the skull make the least resistance.
1771. Encycl. Brit., II. 226/2. The [Columba] turbita, with … a short bill, and a plain vertex.
1840. E. Wilson, Anat. Vade M. (1842), 43. The skull … is divisible into four regions,—a superior region or vertex, a lateral region, an inferior, and an interior region.
1873. Coues, Birds N. W. (1874), 281. That the young males have more or less of the vertex red or yellow, instead of an occipital crescent of scarlet.
1888. P. L. Sclater, Argentine Ornith., I. 137. Vertex more or less tinged with rufous.
attrib. 1899. Allbutt’s Syst. Med., VII. 482. In these vertex cases [of tuberculous meningitis]. Ibid., VIII. 8. The forceps was employed fifteen times in vertex presentations.
b. Ent. (See quots.)
1826. Kirby & Sp., Entomol., III. 365. Vertex, the horizontal part of the Facies, next the front, that lies behind the eyes and between the temples. Ibid., 487. In Blatta and some other Orthoptera the posterior angle of the head is the vertex.
1861–2. Le Conte, Classif. Coleoptera N. Amer., I. Introd. p. x. The upper surface is divided into regions, the back part being called the occiput, the middle the vertex, and the anterior the front.
1897. W. F. Kirby, in Mary Kingsley, W. Africa, 719. Trichomera insignata.… Face nearly smooth, shining black below the vertex.
4. The top, summit or highest point of something, esp. a hill or structure; the crown of an arch. † Also, a high piece of land, an eminence (obs.).
1645. R. Brooke, Eng. Episc., 21. I am neere the Apex of this question, which yet (Pernassus-like) hath a double Vertex, a twofold toppe.
1691. Ray, Creation, I. (1692), 203. The great diversity of Soyls that are found there, every Vertex, or Eminency, almost affording new kinds.
1762. Falconer, Shipwr., III. 243. Its [an altar’s] vertex thirty cubits from the ground.
1770. Pennant, Brit. Zool. (1777), IV. 142. Patella vulgata.… Vertex pretty near the centre.
1811. Pinkerton, Petralogy, II. 338. I was not more than a hundred and fifty paces distant from the vertex of the cone.
1827. Gentl. Mag., XCVII. II. 9. A conical dome, on the vertex of which is a gilt cross.
1879. Cassell’s Tech. Educ., I. 197/1. The highest point in the intrados is called the vertex or crown.
fig. 1865. Mozley, Mirac., vi. 130. The question whether man is or is not the vertex of nature.
