*Idler pinion.* A small gear, usually placed so it may be moved to be in contact with one or more gears, but is not directly connected up in the line of the gearing. *Ignitable.* The term applied to substances which can be brought to the point of burning or exploding. *Immaterial.* Not important. *Imparted.* Given to something else; transferred over. *Impregnated.* To infuse or saturate with another substance. *Impalpable.* Exceedingly fine. *Impulses.* An action which is irregular or at certain periods. *Impediment.* Something which is in the way. *Impact.* A striking against; a force which contacts with another. *Incline.* A declivity; a slope. *Induction coil.* A core with two windings thereon, one of coarse and one of fine wire, so as to change a current from a low voltage to a high voltage, and from a high amperage to a correspondingly low amperage. *Ingredient.* The element in a compound. *Inductor.* Any part of an electrical apparatus which acts on another by induction. *Inflation.* The stimulation or the arousing to unnatural action. The enlarging of a substance. *Inflammable.* Any substance which will burn is called inflammable. *Intervening.* Between; intermediate certain things, or parts. *Integral.* A part of; different parts of a machine which are of the same substance. *Intersection.* To divide at a certain point. The crossing point of one line over another. *Interrupter.* A piece of mechanism which cuts out an electric current at regular intervals. *Interposed.* Placed before; coming between. *Intimate.* Very close. Nearly related. *Insidious.* An influence, not of the best. *Internal, expanding.* Referring to the condition of a gas within an internal combustion engine. *Internal cone.* A clutch which has a cone within the wheel, to receive a part which contacts with it.