Machine. Any instrument, either simple or compound, by which any mechanical effect is produced. A needle, and a clock, are both machines.
Magic Lanthorn, or Lantern. An optical instrument, by which transparent pictures, painted upon glass, are magnified and exhibited on a white wall or screen, in a darkened room. The phantasmagoria, is a species of magic lanthorn.
Mathematics. The science of numbers and of extension. Common arithmetic, is a lower branch of the mathematics. In its higher departments, it extends to every thing which is capable of being either numbered or measured.
Matter. Substance. Every thing with which we become acquainted by the aid of the senses; every thing however large, or however minute, which has length, breadth, and thickness.
Mechanics. That science which investigates the principles, upon which the action of every machine depends; and teaches their proper application in overcoming resistance, and in producing motion, in all the useful purposes to which they are applied.
Medium. In optics, is any body which transmits light. Air, water, glass, and all other transparent bodies, are media. Medium also denotes that in which any body moves. Air is the medium which conveys sound, and which enables birds to fly.
Melody. A succession of such single musical sounds, as form a simple air or tune.
Mercury. That planet which is nearest to the sun. Quicksilver, a metal, which remains fluid at the common temperature of the atmosphere. It is capable of being rendered solid, by intense cold.
Meridian. Midday. A meridian line, is one which extends directly from one pole of the earth to the other; crossing the equator at right angles. It is therefore half of a great circle. The hour of the day is the same at every place situated on the same meridian. Longitude is measured from any given meridian, to the opposite meridian. Places at the same distance in degrees, to the east or west of any meridian, have the same longitude.
Microscope. An optical instrument, by which minute objects, are magnified, so as to enable us to perceive and examine such as could not be seen by the naked eye.