=Lepidodendron= (_lep-i-dō-den´dron_).--Coal-plants, belonging to the Lycopods, of which very many remains are found in coal.
=Lepidosteus= (_lep-i-dŏs´te-us_).--Bony-pike fish, the fossil remains of which are found in rocks and earth strata.
=Lightning= (_līt´nĭng_).--A discharge of atmospheric electricity, accompanied by a vivid flash of light, commonly from one cloud to another, sometimes from a cloud to the earth. The sound produced by the electricity in passing rapidly through the atmosphere constitutes thunder.
=Lithology= (_li-thŏl´ō-jy̆_).--The science which treats of rocks, as regards their mineral constitution and classification, and their mode of occurrence in nature.
=Lode= (_lōd_).--A metallic vein; a longitudinal fissure or chasm filled with ore-bearing matter and having well-defined side walls; lode, lead, vein and ledge are synonymous; a mineral vein in the rock.
=Mastodon= (_mas´tō-don_).--An extinct elephant-like mammal of America, whose teeth have a nipple-like surface.
=Metallurgy= (_mĕt´al-ler-jy̆_).--The art of working metals, comprehending the whole process of separating them from other matters in the ore, smelting, refining and parting them; sometimes, in a narrower sense, only the process of extracting metals from their ores.
=Meteorology= (_mĕ-tē-er-ŏl´o-jy̆_).--The science which treats of the atmosphere and its phenomena, particularly of its variations of heat and moisture, of its winds, storms, etc.
=Min´er-al´o-gy= (_mĭn-er-ăl´ō-jy_).--The science which treats of minerals, and teaches how to describe, distinguish, and classify them.
=Mist= (_mĭst_).--Visible watery vapor suspended in the atmosphere, at or near the surface of the earth; fog.
=Monsoon= (_mŏn-sōōn´_).--A wind blowing part of the year from one direction, alternating with a wind from the opposite direction--a term applied particularly to periodical winds of the Indian Ocean, which blow from the southwest from the latter part of May to the middle of September, and from the northeast from about the middle of October to the middle of December.
=Oceanography= (_ō´shan-ŏg´rȧ-fy̆_).--A description of the ocean.
=Oceanology= (_ō´shan-ŏl´ô-jy̆_).--That branch of science which relates to the ocean.