AN G 



AN G 



ANGEI'OCARPOUS {dyyelov, a ves- 

 sel, KapTTOf, fruit). A term applied by 

 Mirbel, in Carpology, to those plants 

 ■which have their fruit seated in enve- 

 lopes not forming part of the calyx : as 

 the filbert, which is enveloped in a husk; 

 the acorn, which is seated in a cupula. 



ANGEI'OSFE'RMIA [dyyeTov, a ves- 

 sel, arrepida, seed). A term applied to 

 all those plants which have their seeds 

 enclosed in a vessel, or pericarp, as dis- 

 tinguished from those which have no 

 such protection, and are termed gymno- 

 spermia. Thus, the leguminosa; are 

 angeiospermous, the coniferae gymno- 

 spermous. 



A'NGLE {angulus, a corner). A plane 

 angle, according to Euclid, is " the in- 

 clination of two lines to one another, 

 which meet together, but are not in the 

 same direction." The point at which 

 they meet is called the vertex of the 

 angle ; and the angle, there formed, is 

 greater or less, according as the lines 

 torming it diverge more or less from each 

 other. 



I. In Mathematics. 



1. A Right Angle is formed when one 

 straight line meets another straight line 

 perpendicularly, and it contains 90 de- 

 grees, or the quarter part of a circle. An 

 obtuse angle is that which is greater than 

 a right angle ; an acule angle, that which 

 is less than a right angle. 



2. Angle, Spherical. In Trigonometry, 

 the angle formed by the meeting of two 

 lines on the surface of a sphere or globe. 

 Trace any two meridians on the terres- 

 trial globe, as those of London and Peters- 

 burg, from the equator northwards ; 

 they will meet at the north pole, and 

 there form a spherical angle, which, 

 measured on the equator, will be found 

 equal to 30°, 



3. Angle, Solid. The angle formed by 

 three or more planes which meet at the 

 same point, as the angles of solid 

 bodies. 



4. Angle, Re-entrant. An angle whose 

 vertex is turned inwards, and which is 

 consequently greater than two right 

 angles. It is, in fiict, a convex angle. 



5. Angle of Contingence, or Contact. 

 The angle made by a curved line and its 

 tangent to it, at the point of contact. 



6. Angle, Rectilinear, Curvilinear, Mix- 

 tilinear. 1. The first is formed by the 

 inclination of t*o right lines to each 

 other, which meet together, but are not 

 in the same right line. 2. The second is 

 formed by the tangents of two curves, 



26 



where they meet each other. 3. The 

 third is formed by the meeting of a right 

 line and a curved line. 



7. Angles, Adjacent and Contiguous. 

 1. When a side of one angle, being pro- 

 duced, forms a side of another, the two 

 angles are said to be adjacent. Hence, 

 adjacent angles are supplements to each 

 other, making together 180°, or two right 

 angles. 2. When two angles have the 

 same vertex, and one side common to 

 both, they are said to be contiguous. 



8. Angles, Opposite and Alternate. 

 1. When two angles have their sides mu- 

 tually continuations of each other, they 

 are said to be vertical or opposite, and it 

 may be shown that opposite angles are 

 equal, because they have a common sup- 

 plement. 2. The angles which are made 

 on the opposite t^ides of a line cutting 

 two parallel lines, are called alternate. 



9. Angles, Supplemental and Comple- 

 mental. 1. When two angles are toge- 

 ther equal to two right angles, they are 

 said to be supplemental, and one is called 

 the supplement of the other. 2. When two 

 angles are together equal to a right angle, 

 they are said to be complemental, and one 

 is said to be the complement of the other. 



II. In Optics. 



10. Angle of Vision. The angle con- 

 tained between lines coming from op- 

 posite parts of an object and meeting in 

 the eye. On the magnitude of this angle 

 depends the apparent magnitude of all 

 objects perceptible to the sight. 



11. Angle of Incidence. The angle 

 contained between the line described 

 by the incident ray, and a line per- 

 pendicular to the surface on which the 

 ray strikes, raised from the point of in- 

 cidence. • 



12. Angle of Reflection. The angle 

 contained between the line described by 

 the reflected ray, and a line perpen- 

 dicular to the reflecting surface, at the 

 point from which the ray is reflected. 



13. Angle of Refraction. The angle 

 contained between the line described by 

 the refracted ray, and a line perpendicu- 

 lar to the refracting surface at the point 

 in which the ray passes through that 

 surface. 



III. In Astronomy. 



H. Angle at the Sun. The angle under 

 which the distance of a planet from the 

 ecliptic appears at the sun. 



15. Angle of Longitude. The angle 

 formed by the circle of a star's longitude 



