One of the very best forms of lamp is that known as the "student's
reading-lamp," which is, in the burner, an Argand. Provide small lamps
with handles for carrying about, and broad-bottomed lamps for the
kitchen, as these are not easily upset. Hand and kitchen lamps are
best made of metal, unless they are to be used by very careful persons.
Sperm-oil, lard, tallow, etc., have been superseded to such an extent
by kerosene that it is scarcely worth while to give any special
directions in regard to them. In the choice of kerosene, attention
should be paid to two points: its _safety_ and its _light-giving
qualities_. Kerosene is not a simple fluid, like water; but is a
mixture of several liquids, all of which boil at different temperatures.
Good kerosene oil should be purified from all that portion which boils
or evaporates at a low temperature; for it is the production of this
vapor, and its mixture with atmospheric air, that gives rise to those
terrible explosions which sometimes occur when a light is brought near
a can of poor oil. To test the oil in this respect, pour a little into
an iron spoon, and heat it over a lamp until it is moderately warm to
the touch.
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