MAR 



MEA 



ratus for detecting the presence of arseni- 

 ous acid in solution. 



MARSUPI A'TA {marsupium, a pouch). 

 Marsupial animals; an order of Mam- 

 malia, having a sack or pouch under the 

 belly in which they carry their young, as 

 the kangaroo and opossum. They are 

 ovo-viviparous animals, being interme- 

 diate between the truly viviparous mam- 

 malia, and the oviparous birds and rep- 

 tiles. 



MA'RTIAL. An old mythological de- 

 signation of several preparations of iron, 

 from Mars, the god of war. Hence we 

 have martial ethiops, or the protoxide ; 

 martial pyrites, or the sulphuret. 



MASS {/jidaarofiai, to knead together). 

 In physics, a term synonymous with 

 quantity : thus, the mass of a body is the 

 quantity of matter it contains. The mass 

 and density of bodies are estimated ac- 

 cording to their various degrees of poro- 

 sity. The mass represents the number 

 of material particles in a body : the 

 greater the mass, the less porous is the 

 substance. Density, on the contrary, 

 expresses the relation of the masses 

 when the volumes are equal : i. e. "of 

 two bodies that is the more dense, which 

 with equal bulk contains the greater mass." 



MASSES, GLOBULAR. Nodules. 

 These terms are applied, in Geology, to 

 rocks of irregular form, varying from a 

 foot to a mile or more, and imbedded 

 either in a stratified or a massive rock. 

 Irregular masses are rocks of no deter- 

 minate form, and of any size, as granite, 

 greenstone, porphyry. 



MA'SSICOT. Yellow oxide, or pro- 

 toxide of lead. When partially fused by 

 heat, it is called litharge. 



MA'STODON (/iao-Top, abreast, hdovs, 

 a tooth). A genus of fossil extinct qua- 

 drupeds, allied to the elephant, and so 

 called from the form of the hind teeth, 

 or grinders, which have their surface 

 covered with conical mammillary crests. 



MATER ACETI. Mother of Vine- 

 gar; a mould- plant, belonging to the 

 genus mycoderma, which is developed 

 in vinegar, and forms thereon a thick 

 leather-like coat, similar to the inflam- 

 matory crust which covers the crassa- 

 mentum of blood drawn from rheumatic 

 patients. < 



MATE'RIALISM. A philosophical 

 system which refers all existence, in- 

 cluding the nature of the mind or soul 

 itself, to a modification of matter. By 

 this system the brain is supposed to se- 

 crete thought, as the liver secretes bile. 

 211 



MATHEMA'TICS (^a^no-tf, learning). 

 The science which teaches the properties 

 of numbers and of figures. It is, accord- 

 ingly, divided into two branches, viz. 

 arithmetic, the science of number, and 

 geometry, the science of figure. 



Mixed Mathematics denotes mathema- 

 tical reasoning upon facts in nature, and 

 is so named in contradistinction to pure 

 or abstract mathematics, which is em- 

 ployed in reasoning on figures and num- 

 bers, without reference to facts in nature. 



MATRASS. A cucurbit, or vessel of 

 glass, porcelain, or metal, usually of a 

 globular shape, and open at the top, for 

 the chemical purposes of digestion, eva- 

 poration, &c. See Alembic. 



MATRIX. Gangue. The earthy or 

 stony matter which accompanies ores, or 

 envelopes them in the earth. 



MATTER. The general designation 

 of whatever occupies space, and possesses 

 extension and impenetrability : all bodies 

 are matter with fixed boundaries. The 

 physical and chemical properties of matter 

 have given rise to two branches of 

 science, viz. physics and chemistry. 



MAXILLO'SA {maxilla, a jaw). A 

 group of Crustaceous animals, in which 

 the mouth is furnished with jaws, as dis- 

 tinguished from the Edentata, in which 

 the mouth is prolonged in the shape of 

 a sucker. These two groups are pre- 

 cisely analogous to those of the mandi- 

 bulata and the haustellata among insects. 



MA'XIMA and MI'NIMA. These 

 terms, simply signifying "the greatest" 

 and "the least," are employed, in ana- 

 lysis, to signify not the absolute greatest 

 and least values of a variable quantity, 

 but the values it has when it ceases to 

 increase, and begins to decrease, and vice 

 versd. A variable quantity may, there- 

 fore, have many maxima and minima, as 

 the highest and lowest points at which 

 the mercury stands in a barometer at 

 different times. 



MEAN QUANTITY. In Mathema- 

 tics, the mean of two or more quantities 

 is a quantity of intermediate value, found 

 by determinate rules. There are several 

 modes of finding a mean quantity. 

 Thus :— 



1. The arithmetical mean of several 

 quantities is simply the average found by 

 dividing the sum of all the quantities by 

 their number ; and this is the mean al- 

 ways understood, unless another kind be 

 specified. Thus, if three measures of 

 the same length give 122, 123, and 123-4, 

 the average or arithmetical mean is 122*8. 



