e at the
same time a minimum to obviate loss in stack gases.

3rd. The mixture must be burned in a furnace where a refractory material
radiates heat to assist in the combustion, and the furnace must stand up
under the high temperatures developed.

4th. The combustion must be completed before the gases come into contact
with the heating surfaces or otherwise the flame will be extinguished,
possibly to ignite later in the flue connection or in the stack.

5th. There must be no localization of the heat on certain portions of
the heating surfaces or trouble will result from overheating and
blistering.

The first requirement is met by the selection of a proper burner.

The second requirement is fulfilled by properly introducing the air into
the furnace, either through checkerwork under the burners or through
openings around them, and by controlling the quantity of air to meet
variations in furnace conditions.

The third requirement is provided for by installing a furnace so
designed as to give a sufficient area of heated brickwork to radiate the
heat required to maintain a proper furnace temperature.

The fourth requirement is provided for by giving ample space for the
combustion of the mixture of atomized oil and air, and a gas travel of
sufficient length to insure that this combustion be completed before the
gases strike the heating surfaces.

The fifth requirement is fulfilled by the adoption of a suitable burner
in connection with the furnace meeting the other requirements. A burner
must be used from which the flame will not impinge directly on the
heating surface and must be located where such action cannot take place.
If suitable burners properly located are not used, not only is the heat
localized with disastrous results, but the efficiency is lowered by the
cooling of the gases before combustion is completed.

Oil Burners--The functions of an oil burner is to atomize or vaporize
the fuel so that it may be burned like a gas. All burners may be
classified under three general types: 1st, spray burners, in which the
oil is atomized by steam or compressed air; 2nd, vapor burners, in which
the oil is converted into vapor and then passed into the furnace; 3rd,
mechanical burners, in which the oil is atomized by submitting it to a
high pressure and passing it through a small orifice.

Vapor burners have never been in general use and will not be discussed.

Spray burners are almost universally used for land practi