M O L 



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M O N 



MOJLY'BDATE or LEAD. The plomb molyb- 

 date of Haiiy ; pyramidaler blaibaryt of 

 Mohs. Yellow lead ore. It is of a yel- 

 low colour, varying from lemon yellow to 

 yellowish brown. Occurs crystallized and 

 massive. Its specific gravity from 6'5 to 

 6*9. Fracture uneven, or imperfectly 

 conchoidal. Slightly translucent, espe- 

 cially at the edges. Before the blow-pipe 

 it decrepitates, and fuses into a dark 

 coloured mass. It consits of oxide of 

 lead 58, molybdic acid 38, oxide of iron 

 2. It is found at Bleyberg, in Carinthia, 

 and in Mexico, in compact limestone. It 

 is sometimes associated with sulphuret of 

 molybdena. 



MOLYBDE'NA. A mineral of a lead-grey 

 colour, occurring in thin flexible leaves. 



MOLYBDE'NUM. (from po\v@t)aiva, Gr.) 

 This metal was discovered by Hielm in 

 1782. Molybdenum is externally of a 

 whitish yellow colour, but its fracture is 

 a whitish grey. Its specific gravity about 

 8-6. It is nearly infusible. It has not 

 been applied to any use. It is obtained 

 from the mineral molybdena in small 

 grains, agglutinated together in brittle 

 masses. 



MO'NAD. (from juomc, Gr. an atom, mo- 

 nade, Fr.) The recent observations of 

 Professor Ehrenberg have brought to light 

 the existence of monads, which are not 

 larger than the 24,000th of an inch, and 

 which are so thickly crowded in the fluid 

 as to leave intervals not greater than their 

 own diameter. Hence he has made the 

 computation that each cubic line, which is 

 nearly the bulk of a single drop, contains 

 500,000,000 of these monads ; a number 

 which equals that of all the human beings 

 on the surface of the globe in one drop of 

 fluid. Monads, which are the smallest of 

 all visible animalcules, have been spoken 

 of as constituting " the ultimate term of 

 animality." 



MO'NAS. A genus of animalcules, the 

 smallest visible. 



MONA'NDRIA. (from (JLOVOQ, one, and avfjp, 

 a man, Gr.) The first class of plants in 

 Linnaeus' s artificial system. The plants 

 of this class have only one stamen ; it is 

 a small class, and contains only two 

 orders. 



MONA'NDRIAN. Belonging to the class 

 Monandria ; having only one stamen. 



MONI'LIFORM. (from monile, a necklace, 

 and forma, form, Lat.) Resembling a 

 necklace. 



MO'NITOR. (monitor, an admonisher, Lat.) 

 A genus of lizards or saurians, species of 

 which are found both fossil and recent ; 

 the recent inhabit the tropics. Cuvier 

 places this genus in the family Lacerti 

 nida. The monitors frequent marshes 

 and the banks of rivers in hot climates ; 



they have received their name from a 

 common but silly notion that they give 

 warning of the approach of crocodiles and 

 caymans by a whistling noise. One spe- 

 cies, the Lacerta nilotica, devours the 

 eggs of crocodiles. Fossil remains of the 

 monitor have been discovered in the 

 strata of Tilgate Forest, in Sussex. 



MONO'CEROS. (from /iovof, one, and fclpag, 

 a horn, Gr.) A name given to the unicorn. 



MONOCOTYLE'DON. (from povoQ, one, and 

 fcoruXj/dwv, aseed lobe, Gr.) Aplantwhich 

 has only one cotyledon or seed-lobe. 



MONOCOTYLE'DONOUS. Those plants, the 

 seeds of which have either only one coty- 

 ledon, or if more, those alternate on the 

 embryo, are called monocotyledonous ; 

 grasses, lilies, aloes, and palms, are ex- 

 amples. Monocotyledonous plants may 

 be at all times recognised, from the cir- 

 cumstance of the veins of their leaves 

 being parallel, while those of dicotyledo- 

 nous plants are reticulated. 



MoNOi/ciA. (from fiovog, one, and ot/eia, 

 a house, Gr.) The twenty-first class of 

 plants in the artificial system of Linnseus. 

 In this class the stamina and pistils are 

 in separate flowers, but growing on the 

 same individual plant. The orders in this 

 class depend upon the circumstances of 

 their male flowers, and are nine or ten in 

 number. 



MONOS'CIOUS. Plants belonging to the 

 class Monoecia, or such as have male 

 flowers, or flowers with stamens, only, 

 and female flowers, or flowers with an 

 ovarium, only, on the same individual 

 plant. 



MO'NODON. (from ^ovodovg, Gr. having 

 one tooth.) The sea unicora, or narwhal, 

 distinguished by its long tusk, or tusks, 

 for there are sometimes two, extended in 

 a horizontal direction. Only one species 

 is known, namely, the Monodon monoce- 

 ros. The monodon belongs to the order 

 Cetacea, class Mammalia. 



MONOPE'TALOUS. (from povoQ, one, and 

 TrsraXov, a petal, Gr.) Flowers are so 

 called which consist of only one leaf or 

 petal ; or when the leaves which compose 

 the corolla are united by their edges ; the 

 convolvulus, honeysuckle, &c. are exam- 

 ples. 



MONOPHY'LLOUS. (from HOVOQ, sole, and 

 QvXkov, a leaf, Gr.) Having one leaf 

 only, or formed of one leaf; applied to 

 calices consisting of not more than one leaf. 



MONOSE'PALOUS. (from /i6vo, sole, and 

 sepal, a word without any derivation, but 

 invented by botanists to distinguish the 

 parts of the calyx from those of the co- 

 rolla.) A term applied to the calyx of a 

 flower, when the sepals which compose it 

 are united by their edges : the pink, con- 

 volvulus, henbane, &c. are examples. 



