MOR 



MOT 



43m. 4.7s. 5. The average nodical month, 

 or interval of time from a node to a node 

 of the same kind, comprises 27d. 5h. 5m. 

 36.0s. The quantities of these months 

 are here reckoned in mean solar days. 



MONTMA'RTRITE. A yellowish 

 massive mineral, found at Montmartre, 

 near Paris, consisting of the sulphate and 

 the carbonate of lime. 



MOOD (in Grammar). A mood ex- 

 presses the manner in which the action 

 or state denoted by the verb exists, as 

 being certain, contingent, &c. 



MOOD (in Logic). The mood of a 

 categorical syllogism is the designation of 

 its three propositions, in the order in 

 which they stand, according to their 

 quantity and quality. Only eleven moods 

 can be used in a legitimate syllogism. 



MOON. A heavenly body which 

 moves round the earth in the period of a 

 lunar month, accompanying the earth, 

 as a satellite, in its orbit round the sun. 

 The average distance of the moon from 

 the earth is 237,000 miles. 



MOON-CULMINATING. A term 

 applied, in astronomy, to those stars 

 which pass the meridian soon before or 

 after the moon. In the nautical almanac, 

 these stars are selected for each day, and 

 their right ascensions are given for their 

 Greenwich meridian transits. 



MOONSTONE. Adularia. Naker 

 felspar, principally found on Mount St. 

 Gothard. It is the israows petuntse of the 

 Chinese, which constitutes the vitrifying 

 ingredient of their porcelain. The fine 

 variety from Ceylon, when cut en caho- 

 chon, is called moonstone. See Sun- 

 stone. 



MORAINE. A mass of debris accu- 

 mulated along the anterior edge and 

 lateral margins of some of the larger 

 glaciers, in the form of a long dyke or 

 parapet, called in the Tyrol trockne 

 muren, and in Savoy moraine. In Ice- 

 land, where the glaciers are called jo^ii/, 

 the moraines are called jokiilsgiarde. 



MORDANT (mordeo, to bite). A sub- 

 stance employed in dyeing, which has an 

 affinity both for the colouring matter and 

 for the stuflf to be dyed ; the combination 

 of the colour with the texture of the 

 stuff is thus aided by a kind of double 

 decomposition. These substances were 

 supposed, in the infancy of the art, to 

 seize the fibres by an agency analogous 

 to that ol the teeth of animals. 



MO'ROXITE. Norwegian apatite; a 

 phosphate of lime, of a blue-green colour, 

 occurring native in combination with 

 225 



fluoride of calcium, in the form of hex- 

 agonal prisms. 



MORO'XYLIC ACID (mopov, the 

 mulberry, fuAov, wood). Moric acid. 

 An acid procured from the bark of the 

 mulberry-tree, forming compounds with 

 salifiable bases, called moroxalates. 



MO'RPHIA {Morpheus, the god of 

 sleep). A vegetable alkali existing in 

 opium, of which it constitutes the nar- 

 cotic principle. 



MORPHO'LOGY (/xop^J;, form, X670f, 

 a description). The history of the mo- 

 difications of form which the same organ 

 undergoes in different animals or plants. 

 See Metamorphosis. 



MORTAR CEMENT. A mixture of 

 lime and siliceous sand, the former being 

 in the state of hydrate or slaked lime. 

 Hydraulic mortar is obtained from con- 

 cretionary masses found in marl, and 

 also in the form of isolated blocks in the 

 bed of the Thames. 



MOSAIC GOLD, {aurum musivum). 

 The alchemical name of the bisulphuret 

 of tin. It is produced in fine flakes of a 

 beautiful golden colour, and is used as a 

 pigment. 



MOSASAU'RUS. The saurian of the 

 Meuse ; a gigantic extinct aquatic lizard, 

 nearly allied to the monitor, and found 

 in the cretaceous series, chiefly on the 

 banks of the Meuse. 



MO'SCHIDiE {moschus, the musk 

 deer). The Musk Deer tribe ; a family 

 of the Ruminantia, differing little from 

 the rest of the order, except in the ab- 

 sence of horns. 



MO'SCHUS. A quadruped resembling 

 the chamois or mountain goat, from 

 which the perfume musk is obtained. 



MOTACILLI'N^ {motacilla, the wag- 

 tail). Motacilline birds, or Wag-tails ; 

 a family of the Cantatrices of Mac Gil- 

 livray, with slender form, rather short 

 neck, and oblong head; readily distin- 

 guished from the allied families by the 

 elongated tail and peculiar form of the 

 wings. 



MOTHER OF PEARL. A term ap- 

 plied to shells composed of alternate 

 layers of coagulated albumen and carbo- 

 nate of lime. 



MOTHER WATER. The liquid 

 which remains when sea water, or any 

 other solution containing various salts, 

 has been evaporated, and the crystals 

 removed. The mother water contains 

 deliquescent salts, and any existing im- 

 purities. 



MOTION. The continued change of 

 L5 



