ADD 



AD H 



■ ACU'LEUS (dim. of acus, a needle). 

 A prickle ; a hard conical expansion of 

 the bark of certain plants, as of the rose. 

 It is distinguished from the thorn or 

 spine by the nature of its tissue : the 

 prickle consists of cellular, the spine of 

 woody tissue. 



ACU'MINATE (acMmew, a sharp point). 

 Pointed ; ending in a tapering, acute point, 

 as the leaf of Salix alba. 



ACU'TE {acutus, sharp). This terra, 

 in Geometry, is opposed to obtuse: an 

 acute angle is that which is less than a 

 right angle, or does not subtend an angle 

 of 90 degrees ; an acute-angled triangle 

 is that which has three acute angles ; an 

 acute-angled cone is that whose opposite 

 sides form an acute angle at the vertex. 

 In Acoustics, the term acute is opposed 

 to grave, and denotes that the sound of 

 the voice or of a musical instrument is 

 raised with respect to some other 

 sound. 



ADA'GIO. An Italian term signifying 

 slowly, and employed to indicate the 

 slowest movement in music. The de- 

 grees of movement are as follows : adagio, 

 very slow; largo, slow; andante, mode- 

 rate ; allegro, quick ; presto, very quick. 



A'DAMANT (a, priv., Sa/uaw, to sub- 

 due). This terra, which simply means 

 unconquerable, is usually applied to the 

 hardest metal, probably suel. By Plato 

 it was applied to a compound of gold and 

 steel. By others it has been referred to 

 the diamond. 



ADAMA'NTINE SPAR. The crys- 

 tals of Corundum, so named from their 

 approaching to adamant in hardness. It 

 is a variety of crystallized alumina, nearly 

 resembling the sapphire in composition, 

 and is usually found in granite, and 

 sometimes in primary limestone. 



ADDITION {addo, to give to. The 

 operation of adding, or taking together, 

 any numbers or magnitudes, with the 

 view of finding the resulting number or 

 magnitude, which is called their sum. 

 The sign of this operation is -f-, which is 

 readp/M*, or more: thus, a -{- 6 signifies 

 that the number indicated by b is to be 

 added to that indicated by a, and repre- 

 sents the sum of a and b. 



A'DDITIVE and SUBTRACTIVE. 

 Terms sometimes applied to algebraical 

 quantities, in the same sense, respec- 

 tively, as positive and negative, and with 

 the advantage of greater precision of 

 meaning. 



ADDU'^CTOR MUSCLE {adduco, to 

 draw to). A muscle whose office is to 



draw one part of the body to another, as 

 that which closes the two parts of a 

 bivalve shell ; in this case, its base or 

 insertion is indicated by an irregular de- 

 pression in each valve, termed the mus- 

 cular impression. See Abductor. 



ADE'LPHIA (adeA06f, a brother). 

 Literally, a brotherhood ; a term applied 

 in botany to a combination of the fila- 

 ments of the stamens into a single mass. 

 Thus, if there is only one combination, 

 as in Mallow, the filaments are said to be 

 mon-adelphous ; if there are two, as in 

 Pea, they are di-adelphous ; if three, as in 

 some species of St. John's Wort, they are 

 tri-adelphous ; if many, as in Melaleuca, 

 they are called poly-adelphous. The 

 tube formed by the union of monadel- 

 phous filaments is termed, by Mirbel, 

 androphorum. 



A'DEPT {adipiscor, to obtain). A 

 characteristic denomination of those al- 

 chemists, who were supposed to have ob- 

 tained the grand objects of their inquiry, 

 viz. the philosopher's stone and the uni- 

 versal remedy. 



ADFE'CTED or AFFE'CTED. A 

 term applied in Algebra to those equations 

 into which the first or simple power enters 

 as well as the square of the unknown 

 quantity ; thus x^ + 4x = 45. When ap- 

 plied to a quantity, it denotes that the 

 quantity has a co-efiicient, or proper sign ; 

 thus, in the quantity + 5x, the quantity a: 

 is said to be affected with the co-efficient 

 5, and with the positive sign +. See 

 Quadratics. 



ADHE'SION [adhcereo, to stick to). 

 A term denoting, in physics, the force by 

 which bodies, whether similar or dissi- 

 milar, adhere together, when their sur- 

 faces are brought in contact. It differs 

 from cohesion, which denotes the force by 

 which the particles of a body are held 

 together. Adhesion relates to masses, 

 cohesion to molecules : a drop of water 

 maintains its globular form by cohesion ; 

 it moistens other bodies, as lime and 

 sand, by adhesion ; and, on its solidifica- 

 tion in the form of mortar, the adhesion 

 becomes cohesion. 



ADHE'SION, VEGETABLE(orfA^reo, 

 to stick to). A property of vegetable 

 tissue, by which contiguous parts grow 

 together. Opposite leaves may adhere, 

 and become connate ; sepals may adhere 

 entirely, forming a gamosepalous calyx, 

 or partially, and constitute a labiate ca- 

 lyx ; petals may adhere, forming a gamo- 

 petalous corolla ; stamens may adhere, 

 and form an adelphia ; carpels may 



