MIS 



MOL 



MISY. A designation of green vitriol, 

 or sulphate of iron, as it occurs in the 

 form of yellow scales, in the Hartz. 



MI'TRINiE. Mitre-shells ; a sub- 

 family of the Folutidce, or volutes, named 

 from the typical genus mitra ; the spire 

 is always acute, generally longer than the 

 aperture, and the lower plaits smallest ; 

 the foot is small, not dilated on the sides, 

 and the siphon rather long. 



MIXTURE and COMPOUND. In a 

 chemical mixture, the aggregate particles 

 can be separated by mechanical means, 

 and the proportion of the different consti- 

 tuents determined; in a chemical conv- 

 pound, no mechanical power can separate 

 the constituent particles : a new substance 

 is formed, which possesses no properties 

 in common with the original ingredients. 



MNEMO'NICS invrjiJioviKo^!, belonging 

 to memory). A term applied to any sys- 

 tem in which the memory of particular 

 objects is exercised by artificial means. 

 The principle of all such systems is, to 

 associate in our minds two notions, one 

 of which is more easily remembered than 

 the other, but, in consequence of the 

 association, is always followed by that 

 other. I 



MOBI'LITY {mobilis, moveable). A 

 property of matter by which it is capable 

 of being put into motion by the action of 

 a force which is sufficient to overcome 

 its inertia. 



MOCHA STONE. A translucent chal- 

 cedony, containing dark outlines of arbor- 

 ization, like vegetable filaments, and 

 named from Mocha, in Arabia, where it 

 is chiefly found. 



MODAL. In Logic, a modal categori- 

 cal proposition is one which asserts that 

 the predicate exists in the subject in a 

 certain mode or manner, as "accident- 

 ally," " wilfully," &c. 



MODERN EPOCH. In Geology, the 

 present period comprehends all those 

 deposits which owe their origin to causes 

 now in action, and has reference to the 

 phenomena which are taking place at the 

 surface of the earth. See Geology. 



MO'DULUS. 1. In the theory of loga- 

 rithms, the modulus is the number by 

 which all the logarithms in one scale of 

 notation must be multiplied, in order to 

 adapt them to the same number of an- 

 other scale. Thus the modulus of con- 

 version between the common logarithms 

 and the Napierean or hyperbolic scale, is 

 0*43,429,448. 2. In Physics, the modulus 

 of elasticity is a numerical co-efficient, 

 which is constant for the same body, but 

 222 



variable for different bodies ; and which 

 has no influence on the law of elasticity, 

 though it serves to measure its effects. 



MO'HSITE. Crystallized titaniate of 

 iron, found in Dauphiny. 



MOIRE'E METALLIQUE. Crystal- 

 lized tin-plate, obtained by pouring on 

 heated tin-plate a mixture of two parts 

 of nitric acid, and three of muriatic acid 

 diluted with eight parts of water. "When 

 varnished, it is worked into ornamental 

 vessels. 



MOLA'SSE {molle, French, soft). A 

 provincial name for a soft green sand- 

 stone, associated with marl and conglo- 

 merates, belonging to the Miocene Ter- 

 tiary Period, extensively developed in 

 the lower country of Switzerland. 



MOLE'CULAR ATTRACTION. That 

 mode of attraction which operates upon 

 the particles, or molecules, of a body, as 

 distinguished from the attraction of gra- 

 vitation. According to the molecular 

 theory, all bodies are viewed as aggre- 

 gates of minute particles, atwms, or mole- 

 cules, and are formed by the attractive 

 and repulsive forces acting on them at 

 immeasurably small distances. 



MOLECULE (dim. of moles, a mass). 

 A minute particle of a mass or body. 

 It differs from atom, in being always con- 

 sidered as a portion of some aggregate. 



1. Complex organic molecule. An 

 association of two or more binary com- 

 pounds, comparatively simple in consti- 

 tution, often isolable substances and pos- 

 sessed of considerable stability. 



2. Integrant molecules. The name 

 given by Haiiy to the last particles into 

 which the nucleus of a crystal can be 

 mechanically divided. 



3. Molecules, active. Minute moving 

 particles, found in all vegetable matter 

 when rubbed in pieces and examined 

 under a powerful microscope. 



MO'LISITE. The mineralogical name 

 of the crystallized titaniate of iron of 

 Dauphiny. 



MOLLU'SCA (mollis, soft). A terrn 

 employed by Cuvier to designate the 

 fourth grand division of the animal 

 world, and founded upon the unimpor- 

 tant circumstance that the beings to 

 which it is applied have soft bodies, un- 

 supported by any internal or tegumentary 

 framework of sufficient density to merit 

 the name of skeleton. These animals 

 belong to the Hetero-gangliata of Owen, 

 the Cyclo-gangliata of Grant. See Zoo- 

 logy. 



MOLYBDE'NUM (/loAi^ySaor, lead). A 



