(2) HIGH PRESSURE BURNER in which a small jet of high pressure air or steam is used to atomize the oil, the air for combustion being supplied from a source external to the burner. (3) COMBINED HIGH AND LOW PRESSURE BURNER in which the fuel is atomized by high pressure air or steam, and the greater part of the air for combustion is furnished by a blower at a comparatively low pressure. In class (1) the oil is supplied to the burner under pressure and by means of a specially designed jet is thrown against hot baffle plates or gauze screens where the partially broken up liquid is caught by the high velocity air and reduced to a still finer spray by its impact against other screens or baffles further on in the burner. This system is applicable only to the light and intermediate grades of oils, such as gasoline, naptha or kerosene, unless heat is applied to the external casing to aid in the vaporization. In some cases the projection of the burner into the furnace gives satisfactory results, but with such an arrangement there is a tendency to deposit carbon in the burner and for the flame to “strike back” should the velocity of the air fall below a certain critical point. Better results were had with this type of burner, by the author when the air blast was preheated by passing several long lengths of the intake air pipe over a hot part of the furnace, instead of entering the burner nozzle into the combustion chamber proper. A well known modification of this type is the gasoline torch used by electricians and plumbers in which the gasoline is sprayed into a perforated hot tube by air pressure in the tank. When the spray formed at the needle valve strikes the surrounding hot tube it is instantly vaporized and is mixed with the air passing through the perforations in the tube. While the air entering the tube is not forced through the openings by external pressure it attains sufficient velocity to aid in the vaporization because of the vacuum established by the jet. This however is only enough for the more volatile fuels—such as gasoline or benzine. The high pressure which is by far the most commonly used with low grade fuels may be divided into five principal types (a) =ATOMIZER= burner, (b) The =INJECTOR= burner, (c) =DRIP= feed burner, (d) =CHAMBER OR INTERNAL= burner, (e) =EXTERNAL BLAST= burner. All of these burners break up the fuel by high pressure air or steam, the types given being different only in the way that the pressure is applied to the fuel.