Manganese to artensiticalloysteels

Manganese dioxide to Manual arts

aluminium, iron and lead. Used for parts requiring strength and toughness.

Manganese dioxide. (Elec.) A depo­larizing agent used in primary cells.

Manganese steel. (Metal.) Manga­nese steel, containing 0.20 to 0.50 per cent carbon and 1.00 to 1.30 per cent manganese, has a high tensile strength and is frequently used to replace 3Yz per cent nickel steel. An increase of manganese tends to make the steel very brit­tle, but with a still greater increase of manganese the ductility, to a certain extent, returns.

Manganin. (Metal.) An alloy of cop­per, nickel, and ferromanganese. Much used for standard resistance coils.

Mangling. (Textile) The pressing of fabric under heated or unheated rollers.

Manhole. An opening through which a workman may gain access to a drain, boiler, sewer, tunnel, etc., or other underground area.

Manifold. (Auto.) Usually a casting or connection containing several branches or parts, as an exhaust manifold on an automobile engine, for conducting the exhaust from each cylinder into a single exhaust pipe.

Manifold paper. (Print.) A very thin paper, such as "onionskin", used for duplicating.

Manifold vacuum. (Auto.) State of atmospheric tension existing in a manifold when the engine is in operation.

Manila. (Papermkg.) A general term used to describe tan or yellowish paper or paperboard.

Manila tag. (Papermkg.) A stiff paper of good folding properties. It is of a light-buff colour, its shade varying. with the grade.

Manipulation. The act of working skillfully with the hands.

Manometer. (phys.) An instrument for measuring elastic pressure, as of gases.

Mansard roof. (Arch.) A roof with a double slope on all four sides, the lower slope steeper than the up­per. . Dormers are frequently in­stalled.

Mansion. (Arch.) A large or preten­tious house. .

Mantel. (Arch. and Masonry) The shelf above a fireplace or attached to a chimney breast; also the fac­ing about a fireplace, including the shelf.

Mantissa. (Algebra) The decimid or fractional part of a logarithm.

Manual. (Shopwk.) (I) Relating to handwork. That which is done by hand. (2) A handbook of instruc­tions.

Manual arts. Work performed with the hands. Manual switch to Martensitic alloy steels

Manual switch. (Auto.) A hand- or foot-operated switch as opposed to one operated in any other manner.

Manuscript. (Print.) Material written by hand or by typewriter. Written copy for the printer.

Maple. (Woodwkg.) A hard, light-col­oured, tough wood much used for flooring and veneers. Mar. To scar or deface.

Marble. (Bldg.) A kind of limestone ranging in colour from white to dark gray and to brown; widely used for both interior and exterior finish of buildings; also for switchboard pan­els. (Papermkg.) Paper resembling marble in appearance.

Marble dust. (Wood Fin.) Crushed and pulverized limestone. Large quantities are used in making putty.

Marbling. (Furn.) Painting wood in imitation of marble. Margin. (Print.) A space along an edge or a bounding line; a border. The space on the edge of a printed sheet, which may be blank or contain notes.

Marginal note. (Print.) Explanatory matter placed in the margin of a page close to the item to which it refers.

Marine glue. (Woodwkg.) A compo­sition of I part crude rubber; 2 parts shellac; 3 parts pitch.

Marking awl. (Furn.) As the name suggests, a pointed steel instrument for "marking out", especially on hardwood.

Marking gauge. (Wood Patmkg.) A woodworker's gauge, used for scribing lines parallel to the edge of a board. It consists of a bar with an inserted pin or scribe, and a slid­ing head which may be adjusted by means of a thumb screw.

Marking knife. (Furn.) A knife used as the marking awl, especially for softwoods.

Marking machine. (Shop wk. ) A machine for stamping trade-marks, patent dates, etc., on cutlery, gun barrels, etc. Stamps are usually on rolls and are rolled into the work.

Marl. (Geol.) A rich, limy earth used principally to condition soils defi­cient in lime.

Marquetry. (Woodwk.) An ornamen­tal surface. built up of pieces of various hardwoods to form a pat­tern. Occasionally ivory, bone, mother-of-pearl, etc., also are used.

Marsh gas or methane. (Chem.) (Ch4) A light, odourless, inflam­mable, gaseous hydrocarbon, occuring naturally as a product of decomposition of organic matter in marshes and mines, or produced artificially by dry distillation of many organic substances. It consti­tutes about 30 per cent of coal gas and from 90 to 95 per cent of natural gas.