ALT 



ALU 



ALOE'TIC ACID. The bitter prin- 

 ciple of aloes ; a precipitate procured by 

 heating nitric acid on aloes. 



ALPHABET. A term derived from 

 the first two letters of the Greek lan- 

 guage, alpha, beta, or from the cor- 

 responding HebreAV letters, aleph, beth; 

 and applied to the series of letters used 

 in different countries. The term corre- 

 sponds with our familiar expression, the 

 A, B, C ; and some writers have assigned 

 an analogous origin to the Latin name 

 given to the letters, viz. elementa, which 

 corresponds with the pronunciation of 

 the three liquids, /, m, n. 



ALPHAORCEIN ; BETAORCEIN. 

 Terms applied by Dr. Kane to two sub- 

 stances composing the orcein of archil : 

 the latter is produced by oxidation of the 

 former, and is the orcein of chemists. 



A'LPHERATZ. A star of the second 

 magnitude in the head of Andromeda. 



ALPHO'NSINES. A series of astro- 

 nomical tables drawn* up by order of 

 Alphonso X. of Castile, in the year 1252. 

 They contain the places of all the fixed 

 stars, and all the methods and tables 

 then in use for the computation of the 

 places of the planets. 



ALPINE PLANTS. Plants which 

 grow naturally in mountainous situa- 

 tions, where they are covered with snow 

 during the winter. 



ALSINA'CEiE. The Chickweed tribe 

 of Dicotyledonous plants. A section of 

 the Caryophyllaceae, in which the sepals 

 are disunited. See Silenacece. 



A'LTAN. A star of the first magni- 

 tude in the northern constellation Aquila, 

 the eagle with Antinous. 



A'LTERATIVES {altera, to change). 

 Remedies which produce a change. Re- 

 medies which very gradually re-establish 

 the health, as a drop of water, by fre- 

 quently falling, hollows a stone. 



ALTE'RNATE {alternatus, changed 

 by turns). A term applied in geometry 

 to the angles which are made by two lines 

 with a third, on opposite sides of it. In 

 algebra, those terms of a proportion are 

 said to be alternate, which are separated 

 from one another by another term : thus, 

 in the proportion 



2 : 4 : : 8 : 16, 



2 and 8 are alternate terms, as also are 

 4 and 16. If alternate terms be rendered 

 consecutive, and consecutive terms alter- 

 nate, the proportion is still maintained: 

 thus, 



2 : 8 : : 4 : 16. ^ 



This relation is referred to in the fifth 

 19 



book of Euclid by the Latin word alter- 

 nando, which signifies " by alternation," 

 or alternately. 



1. Alternate, in Botany. That position 

 of leaves upon the stem, in which one 

 leaf is placed above or below another, 

 and on the opposite side. The term is 

 generally employed in distinction to oppo- 

 site, or that arrangement in which two 

 leaves are developed from the same plane. 



2. Alternately pinnate. A term used 

 in botany, where the leaflets of a pinnate 

 leaf are placed alternately on the common 

 petiole, as in potentilla rupestris. 



ALTHE'INE. A supposed new vege- 

 table principle, extracted from the roots 

 of althea officinalis, and found to be iden- 

 tical with asparagin. 



ALTHIO'NIC ACID. An acid found 

 in the residue of the preparation of ole- 

 fiant gas, by means of alcohol and sul- 

 phuric acid, and named from the words 

 alcohol and ethionic. 



A'LTITUDE {altus, high). A term 

 applied in Astronomy to the angle of 

 elevation of a celestial body above the 

 horizon, measured in the arc of that 

 vertical circle which passes through the 

 body. 



1. The apparent altitude of a star is 

 the angle found by immediate observa- 

 tion ; the real altitude is ascertained by 

 correcting the apparent altitude for re- 

 fraction, parallax, &c. 



2. The altitude of the pole is the geo- 

 graphical latitude of the place of observa- 

 tion, and remains the same throughout 

 the twenty-four hours. 



3. In Geometry, the term altitude is 

 synonymous with height. Thus, the alti- 

 tude of a triangle is measured by the 

 straight line drawn from the vertex per- 

 pendicular to the base ; that of a cone, by 

 the straight line drawn from the vertex 

 perpendicular to the plane of the base ; 

 that of a parallelogram, by the perpen- 

 dicular drawn from its base to the oppo- 

 site side; that of a prism, by the perpen- 

 dicular distance between its bases. 



A'LUDEL. A pear-shaped vessel re- 

 sembling the alembic, and used by the 

 old chemists in the process of sublima- 

 tion. 



A'LULA (dim. of ala, a wing). A 

 little wing. 



A'LUM. Alumen. A salt consisting 

 of a ternary compound of alumina, or 

 pure argillaceous earth, potass, and sul- 

 phuric acid. Alum is the base of pure 

 iclay. The indurated beds of clay em- 

 ployed for obtaining the alum are called 



