Ichnology is the scientific study of footprints, first popularised in the 19th century following the discover in 1828 of the footprints of a tortoise in sandstone at Annandale by Dr. Duncan.
Igneous rock — Igneous rock is rock formed from cooling lava.
Iodine — Iodine is a non-metal element with the symbol I.
Ion — An ion is a charged atom or group of atoms. The charge occurs from a surplus or deficiency of electrons.
Isotope — An isotope is a form of an element which has a different atomic weight and nuclear properties than other isotopes of the same element.
Jurassic — The Jurassic was the tenth geological period, 135,000,000 years ago. The first mammals evolved.
Krypton — Krypton is a gaseous element with the symbol Kr.
Lava — Lava is the molten material expelled by a volcano. It cools to form igneous rock.
Long Waves — Long Waves are radio waves having wavelengths between 1000 and 10,000 meters, corresponding to frequencies from 300 khz down to 30 khz.
Magnesia — see "Magnesium oxide"
Magnesian — see "Magnesium oxide"
Magnesium oxide — Magnesium oxide is formed when magnesium is burnt in the air. It is a white powder that is used to treat acidity in the stomach.
Magnesium Peroxide — Magnesium peroxide is a white, tastless, water-insoluble powder used as an antiseptic and as an oxidizing and bleaching agent.
Magnesium Silicate — Magnesium Silicate is a fine, white, odourless, tastless powder with variable hydration. It is insoluble in both water and alcohol and is used as a rubber filler, a bleaching agent, and odour absorber and in the manufacture of paints and resins.
Magnesium Sulphate — see "Epsom Salts"
Magnesium Trisilicate— Magnesium Trisilicate is a fine, white, odourless, tastless powder used in industry as an odour absorber and as a decoloriser. It is used in medicine as an antacid.
Magnet — A magnet is a piece of one of the so-called ferromagnetic materials which has been magnetized, that is to say it has acquired, either permanently or temporarily, the power of attracting or repelling other pieces of similar material and of exerting a mechanical force on a neighbouring conductor carrying an electric current.
Magnetostriction — Magnetostriction is small changes in the length of a piece of magnetic material which accompany the process of magnetization.
Magnetron Effect — The magnetron effect is the deflexion of electrons emitted from a straight filamentary or thin tubular thermionic cathode and accelerated towards a co-axial cylindrical anode, the deflexion resulting from the application of an axial magnetic field.
Mass — In physics, mass is the quantity of matter which a body contains.
Mendelevium — Mendelevium is an artificial metal radioactive element with the symbol Md.
Mercuric cyanide — Mercuric cyanide is a very poisonous compound prepared by dissolving yellow mercuric oxide in aqueous hydrocyanic acid.
Mercury fulminate — Mercury fulminate is an explosive used in detonators and percussion caps.
Metal — Metal is a class of elements.
Meteor — A meteor is a small solid body which sails through space.
Meteorite — A meteorite is a piece of rock or metal from space.
Mineral — A mineral is an element or compound occurring naturally due to inorganic processes.
Miocene — The Miocene was the sixteenth geological period, 25,000,000 years ago. The first apes evolved.
Molecule — A molecule is the smallest particle of any substance that can exist and still exhibit the properties of the substance.
Moroxite — Moroxite is the crystallised form of apatite, occurring in crystals of a brownish or greenish-blue colour.
Mu-metal — Mu-metal is a nickel-iron alloy characterised by its high permeability at low field strengths and its small hysterisis losses.
Nickel Silver — Nickel Silver (German Silver, Pack-Fong) is an alloy of copper, nickel and zinc in different proportions. Sometimes lead is added if the alloy is destined for making candlesticks or casts.
Niobium — Niobium is a metal element with the symbol Nb.
Nitrate — A nitrate is any salt of nitric acid.
Nitro-glycerine — Nitro-glycerine is a powerful explosive produced from nitric acid and glycerol.
Nitrogen — Nitrogen is a gaseous element with the symbol N. It comprises 79 percent of the air.
Nobelium — Nobelium is a radioactive metal element with the symbol No.