MER 



MET 



English reckon from London, or the 

 Royal Observatory at Greenwich, the 

 French from Paris, the Spanish from 

 Madrid, &c. On the celestial globe the 

 meridian is represented by the brass 

 circle perpendicular to the horizon. 



1. Meridian Altitude. The altitude, 

 or height above the horizon, in degrees, 

 of any celestial object, when it crosses 

 the meridian of a place. 



2. Meridian, Magnetic. The magnetic 

 meridian, as pointed out by the mariner's 

 compass, differs from the geographical (or 

 real north and south) by the amount of 

 the variation of the compass. In other 

 words, if we conceive a vertical plane to 

 be drawn through the axis of a magnetic 

 needle when in a state of rest, we have 

 the magnetic meridian for the particular 

 place where the needle is. See Dip of 

 Magnetic Needle. 



MERITHA'LLUS {fxepoi, a part, OaX- 

 X6t, a young shoot). The terra applied 

 by Du Petit Thouars to the internodium 

 of other writers, denoting that portion of 

 the axis of a plant which is between two 

 nodes. 



MEROTIDiE {merops, the bee-eater). 

 The Bee-eaters ; a family of the Inses- 

 sores, or Perching birds, belonging to the 

 warmer regions of the Old Continent and 

 its islands ; one species visits this coun- 

 try at irregular intervals. See Fissi- 

 rostres. 



MERULI'DiE {merulus, a thrush). 

 The Thrushes ; a family of the Insessores, 

 or Perching birds, in which the point of 

 the beak is not hooked, and the lateral 

 tooth is not so prominent as in the 

 Laniadse, or Shrikes. See Dentirostres 



MESEMBRYA'CEiE. Ficoidecc. The 

 Fig-marigold tribe of Dicotyledonous 

 plants. Succulent shrubs or herbs with 

 showy flowers ; sepals definite, succu- 

 lent; petals indefinite, linear; stamens 

 indefinite; ovary many-celled; capsule 

 with a starry dehiscence. 



MESITE. A liquid existing in pyro- 

 xylic spirit, and produced in the distilla- 

 tion of wood. Mesiten is a similar pro- 

 duct of the same process. H^sitylene is 

 a light oily liquid, procured by distilling 

 pyro-acetic spirit {acetone) with fuming 

 sulphuric acid. 



MESO- (/ieo-of, middle). The Greek 

 term for middle, or that which is situate 

 between others. 



1. Meso-carp (kopttop, fruit). The in- 

 termediate part of the pericarp of fruits. 

 When fleshy, it is termed sarcocarp. The 

 fibrous portion of the fruit of the cocoa 

 216 



palm is the mesocarp; the eatable part 

 of the cherry or peach is the sarcocarp. 



2. Meso-lahe {Xa^etv, to take). A ma- 

 thematical instrument used by Eratos- 

 thenes for finding mean proportional 

 lines, required in the problem for the 

 duplication of the cube. 



3. Mesa-lite {\i9o<;, a stone). Needle- 

 stone ; a zeolitic substance, consisting of 

 a hydrated silicate of alumina, lime, and 

 soda, and usually referred to mesotype. 



4. Meso phloeum (0\oi6f, bark). That 

 portion of the bark of plants which lies 

 between the epiphloeum and the endo- 

 phlceum, or liber. See Bark. 



5. Meso-phyllum {(pvWov, a leaf). The 

 cellular substance of the leaves of plants, 

 also called diachyma and diploe. 



6. Meso-sperm {airepina, seed). The 

 middle one of the three membranes by 

 which seeds are sometimes enveloped. 



7. Mesa-type (rvTrop, form). A silicate 

 of soda and alumina ; a simple mineral, 

 white, and needle-shaped; one of the 

 zeolite family, frequently found in trap- 

 rocks. To this are referred the natrolite 

 of Klaproth, the needle-stone of Werner, 

 the mesolite, &c. 



META'BOLA {/jLera/SSXn, change). A 

 term applied by zoologists to those genera 

 of insects which undergo metamorphosis, 

 or pass through the larva, pupa, and 

 imago states of insect existence. See 

 Ametabola. 



METACE'NTRE (/uera, a preposition 

 denoting change, Kevrpov, a centre). When 

 the position of equilibrium of a floating 

 body has been disturbed, if the vertical 

 line passing through the centre of buoy- 

 ancy (the line of the thrust of the fluid), 

 when produced upward, meets the axis 

 passing through the centre of gravity, 

 the point of intersection is called the 

 metacentre. 



METAGA'LLIC ACID. A compound 

 obtained by the partial decomposition of 

 gallic acid, when rapidly heated to 480°. 



METALLIC DEPOSITS. By this 

 term, geologists denote metallic matters 

 with which the substance of rocks is fre- 

 quently permeated, in the form of grains, 

 filaments, nodules, irregular plates or 

 veins, and strata or beds. In these cases 

 the metallic matters are supposed to be 

 of contemporaneous origin with the rocks 

 or formations containing them. 



META'LLIC VEINS. Metallic ores 

 and mineral substances found in fissures 

 of rocks which are composed of very 

 diflferent materials. They occur chiefly 

 in the primary, and in the lower and 



