MAG 



M AL 



MAGNETO-ELECTRICITY. A term 

 applied to those electric phenomena which 

 may be produced by magnetism. 



MAGNETO'METER. The term ap- 

 plied by Gauss to a magnetic apparatus 

 consisting of bars of iron from one to 

 four feet in length, and weighing from 

 1 lb. to 25 lbs. These masses are not 

 affected, like the needle, by variations of 

 temperature, nor by the presence of 

 other similar bodies, while at the same 

 time they are capable of indicating the 

 minutest variations in the intensity of 

 the earth's magnetism, by changes in the 

 position of the magnetometer, which can 

 be measured to an angle of one second. 



MAGNE'TOMO'TOR. A voltaic se- 

 ries of two or more large plates, for pro- 

 ducing a great quantity of electricity of 

 low tension, and thus exhibiting the 

 phenomena of electro-magnetism. 



MAGNIFYING GLASS. A convex 

 lens, which increases the apparent size 

 of objects viewed at a small distance 

 through it. It is also termed a burning 

 glass, because, when the sun's rays are 

 brought to a point, after passing through 

 a lens of this kind, they produce a strong 

 heat. 



MA'GNITUDE {magnitudo, size). The 

 general term for quantity of space. In 

 Geometry, it denotes the space occupied 

 by any figure, and has relation to the 

 three dimensions of length, breadth, and 

 thickness. It may, in fact, be applied to 

 any thing which involves the question of 

 "greater or less." 



1. When one magnitude is compared 

 with another of the same kind, the first 

 is called the antecedent, and the second 

 the consequent. 



2. One magnitude is said to be a mul- 

 tiple of another, when it contains that 

 other a certain number of times exactly : 

 and the other magnitude, which is con- 

 tained in the first a certain number of 

 times exactly, is said to be a submultiple, 

 or measure, or part of the first. Hence, 

 also, one magnitude is said to measure 

 another, when it is contained in the other 

 a certain number of times exactly, 



3. Two magnitudes are said to be equi- 

 multiples of two others, when they con- 

 tain those others the same number of 

 times exattly: and the other magnitudes, 

 which are contained in the first the same 

 number of times exactly, are said to be 

 like parts of the first two. Thus, 7 A, 

 7 B, are equimultiples of A, B; and 

 A, B, are like parts of 7 A, 7 B. 



4. Two magnitudes are said to be com- 



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mensurable with one another, when a 

 common measure of the two may be 

 found, that is, a magnitude which is con- 

 tained in each of them a certain number 

 of times exactly. In like manner, any 

 number of magnitudes are said to be 

 commensurable, when there is some mag- 

 nitude which is contained in each of 

 them a certain number of times exactly. 

 Magnitudes which have no common 

 measure are said to be incommensurable. 



MA'GNITUDE, APPARENT. The 

 name given to the angle under which an 

 object appears at the eye, or the angle 

 formed by lines drawn from the extrem- 

 ities of the object to the eye. The idea 

 which we form of the real magnitude is 

 not that which is necessarily conveyed 

 with the first gift of sight, but is gra- 

 dually made out by the help of expe- 

 rience. The sun and moon are nearly of 

 the same apparent size. 



MA'GNITUDE OF STARS. The 

 magnitudes of stars are vaguely derived 

 from their apparent brilliancies. Very 

 brilliant stars, though of varying bril- 

 liancy, are said to be of the first magni- 

 tude ; stars of the next degree of bril- 

 liancy are said to be of the second magni- 

 tude; and so on. Yet there is little 

 perceptible difference between the boun- 

 dary stars of any two adjoining classes, 

 and hence there is no little confusion. 



MA'IIDiE or MA'INS. A tribe of 

 brachyurous crustaceans, or Crabs, named, 

 from the genus maia, or sea-spider, as it 

 is commonly called. 



MAJOR and MINOR. These terms 

 are applied, in Music, to imperfect con- 

 cords, which differ from each other by a 

 semitone. 



MAJOR TERM. In Logic, the Major 

 Term of a syllogism is the predicate of 

 the conclusion. The Major Premiss is 

 the one which contains the major term. 

 In hypothetical syllogisms, the hypotheti- 

 cal premiss is called the major. , 



MA'LACHITE. Green bice. A car- 

 bonate of copper; a green carbonate, 

 occurring with a fibrous structure and 

 velvety appearance, and with a compact 

 structure in the mines of the Uralian 

 mountains. 



MA'LACOLITE. Sahlite. A pyrox- 

 enic mineral, consisting of a silicate of 

 magnesia and lime, found in Shetland, 

 &c. It is a sub-species of oblique-edged 

 augite. 



MALACO'LOGY (/iaXaKo?, soft, Xo-yof, 

 a description). The science of the Mol- 

 lusca, termed by Aristotle malakia, com- 



