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477 
Lithological. The character of a rock or formation considered with re- 
ference solely to its mineral composition. 
Lignite. Wood partially carbonized in the earth ; it usually retains the 
vegetable structure. The change does not seem to have been effect- 
ed by heat, but is the result of some chemical process, as the action 
of pure sulphuric acid in some instances, and of water in others. 
Littoral, of, or belonging to, the shore. 
Loam. A mixture of sand and clay. 
Mural Escarpment. A rocky cKfF, more or less inclined. 
Mammillary. Protuberances on the surface of a mineral, which are 
segments of sphere ; mammae, breasts. 
Mammoth. An extinct species of animal, allied to the elephant. 
Marl. Any mixture of clay and carbonate of lime, which effervesces 
with acids. 
Matrix. Gangue. The mineral mass which is in immediate contract 
with the ore of a metal, both of which constitute a vein. 
Manganese. A hard black mineral, resembling the dark coloured he- 
matites. It is the oxide of manganesium, one of the metals. 
Megatherium. One of the extinct fossil quadrupeds, resembling the sloth. 
Mechanical origin of, Rocks composed of sand, pebbles, &c. or sedi- 
mentary rocks generally, are said to have a mechanical origin. The 
term is used in contradistinction to rocks having a crystalline struc- 
ture, which have a chemical origin. 
Mica. Sometimes called isinglass. A mineral, which may be split into 
numerous elastic laminas. 
Mica slate. A primary rock, composed of fine grains of quartz, and 
generally small scales of mica. It is eminently fissile. 
Miocene. An era or period subsequent to the eocene, and characterized 
by a greater proportion of animals analogous to those now living. 
Deposits formed during this period are termed miocene strata. 
Molusca. Moluscous animals. Those soft animals, whose covering is 
a thick shell, as oyster and clam. 
Monocoiyledonous . One of the grand divisions of the vegetable king- 
dom. It includes the grasses, palms, lihaceas, and whose seed have 
only one lobe. 
Mountain limestone. A series of limestone strata immediately below 
the coal measures. 
Muriate of Soda. The chemical name for common salt, because it is 
composed of muriatic acid and soda. 
Naphtha. A very thin volatile inflammable liquid, of which there are 
springs in some volcanic districts. 
Neiv Red Sandstone. A series of sandy, argillaceous, and often calca- 
reous strata, whose predominant colour is brick red, but contains 
many spots and stripes, which are gray and greenish gray. It is 
therefore sometimes called the variegated sandstone. It overhes the 
coal measures. 
Nucleus. A solid central piece, around which layers of the same or 
other matter has collected. The kernel. 
Old Red Sandstone. A rock belonging to the carboniferous group. 
Oolite. Oolitic. A hmestone composed of rounded grains, like the roe 
