The following classification includes all fuels in general use in the arts and industries. Some of these have but limited and special uses in the metal industries.

(1) Solid Fuels.

(a) Natural Fuels.

Wood.

Peat.

Coal.

(b) Prepared Fuels.

Charcoal. Coke.

Powdered Coal. Briquettes.

(2) Liquid Fuels.

(a) Natural Fuels.

Mineral Oils.

(b) Prepared Fuels.

Refined Mineral Oils. Alcohols.

(3) Gaseous Fuels.

(a) Natural Gas.

(b) Prepared Gases.

Producer Gas. Water Gas. Illuminating Gas.