105. The mineral oils, called paraffin or petroleum oils, are the cheapest oils in use They contain a very great amount of carbon or charcoal, and if they are burned without a chimney this escapes into the air in dark clouds of black smoke. These oils, therefore, require to be burned in a properly constructed lamp, so that sufficient air shall be sent against the flame to consume all the carbon.
The best paraffin lamps are those with a single flat wick, which is able to be turned to any required height above the wick tube A, by small toothed wheels turned by a handle, B. The large quantity of air required by the flame rises up through the cone or cap C, and is directed against the sides of the flame, producing a complete combustion of the carbon, and a very brilliant light.
Paraffin or petroleum oils were formerly sold containing much volatile inflammable spirit. At the present time no mineral lamp oil must be sold which is dangerous.
Petroleum lamps are perfectly free from danger if properly used. The oil-holder should be of glass, as if made of metal, it is apt to become heated. The lamps should always be filled before dark, and never after being lighted.
Any oil spilled on the outside should be carefully wiped off, or it will produce a disagreeable smell when the lamp is used. To light a petroleum lamp the glass chimney should be removed, then the wick turned above the slit in the cone, and when lighted instantly turned down again; the chimney should then be put on and the wick turned up so as to produce a large bright flame without smoke, but so as to produce the full flame, when the lamp burns without smell. If the flame is turned down low, there is no saving of oil,