*Manifold.* A series of piping on the engine, so as to bring all the inlet or exhaust pipes together. *Manually.* Operating by hand. *Maximum.* The utmost; the greatest amount or sum. *Mesh.* Fitting together, like the teeth of gear wheels. *Mean Effective Pressure.* That pressure in the movement of a cylinder which represents the average, as the piston moves from end to end of its stroke. *Metallic couples.* Usually two metals of different structure, and of different polarities. *Minimize.* To belittle; the smallest amount. *Misconception.* A wrong idea; a mistaken view. *Misnomer.* A false name; a wrong appellation. *Minutely.* Very accurate; correct to the smallest feature. *Momentarily.* For an instant only. *Momentum.* That quality of matter which is the combined energy of mass and speed. Inertia. *Multi-cylinder.* More than one; several put together. *Multiple.* Containing or consisting of more than one. *Multiple disk.* A form of clutch where there are a number of disks which contact with one another. *Muffler.* A device for silencing the noise of the explosion of the engine. *Neutral.* Neither. *Normal.* The usual form, manner, or condition. *Obliquely.* Branching off from a straight line, at an angle. *Obstruction.* Something in the way. *Operation.* A process; an act, or a manner of doing a thing. *Oxygen.* The life giving element in the atmosphere. One-third of water is oxygen; one-fifth of the atmosphere is oxygen. *Parallel.* The same distance apart all along. *Pedestrian.* A footman; a walker. *Perceptible.* That which can be observed with our senses. *Perimeter.* The outer margin of a wheel; the bounding line of any figure of two dimensions. *Pedal.* A foot operated lever. *Permanent magnet.* A bar of steel, charged with magnetism which it retains indefinitely.