CARBURETER TYPES.--There are two distinct types of carbureters, one in which the gasoline is forced out through a very fine nozzle, and at the ejecting point is mixed with a current of air which passes to the engine cylinders, and this is designated as the _spraying_ device. The other form of construction depends for carbureting the air on exposing a large body of the gasoline to a passing blast of air, and is called the _surface_ type. THE SPRAYING CARBURETER.--As most cars now use the spraying system, that type will be considered first. There is no special form of nozzle required to eject the fuel, and the distinctive features of the various designs has been to produce positive and regular feed and to assure the proper mixture at all times during the operation of the engine. DISSECTING THE CARBURETER.--For the purpose of making each particular part of a carbureter clear and distinct, let us build up one, so that special attention may be directed to the various operative elements. A cored cylindrical casting A, Fig. 78, is provided, which has a large opening in its lower end that is closed by a plug B. This plug has an upwardly-extending tubular projection B´. The upper end of the cylinder has a cap C, open centrally, and having an opening formed by a downwardly-projecting tube D, and this has a contracted throat as at E. THE MIXING CHAMBER.--The exterior of the downwardly-projecting cap tube, is turned up true, and fits into the tubular extension B´. The particular feature of this sketch is to show the adjustment of the needle valve which admits the gasoline, and the relative position of the float. [Illustration: Fig. 78. Carbureter Float and Needle.] THE FLOAT CHAMBER.--The circularly-formed chamber G, within which the float operates, contains the liquid fuel. The inner end of the plug B has a cross duct I, and centrally is an upwardly-projecting tubular extension J, the bore being flaring, as shown, and in this the needle valve K rests and is made adjustable at its upper threaded end. When the needle valve is raised, gasoline flows through the duct I upwardly past the flaring orifice, in J, and air is permitted to flow in through the openings I around the central tube J, so that the air and gasoline meet above the upper end of the tube. THE VENTURI TUBE.--The inwardly-projecting part E constitutes what is called a venturi tube, the upwardly-rushing air between the contracted opening formed around the tube at this point being such that when the two fluids meet and spread out in the enlarged opening above, the particles of gasoline are not only broken up minutely, but are intimately mixed with the air. [Illustration: Fig. 79. Carbureter Inlet Valve.]