If the water-supply is mainly controlled by a needle-valve, it
is useful to connect the burner with the carbide vessel through a short
length of rubber tube; and if this plan is adopted, a cock can, if
desired, be put close to the burner. The rubber should not be allowed to
form a bend hanging down, or water vapour, &c., may condense and
extinguish the flame. In any case there should be a steady fall from the
burner to the decomposing chamber, or to some separate catch-pit for the
products of condensation. Much of the success attainable with small
generators will depend on the water used. If it is contaminated with
undissolved matter, the dirt will eventually block the fine orifices,
especially the needle-valve, or will choke the pores of the wick or the
felt pad. If the water contains an appreciable amount of "temporary
hardness," and if it becomes heated much in the lamp, fur will be
deposited sooner or later, and will obviously give trouble. Where the
water reservoir is at the upper part of the lamp, and the liquid is
exposed to the heat of the flame, fur will appear quickly if the water is
hard. Considerable benefit would accrue to the user of a portable lamp by
the employment of rain water filtered, if necessary, through fabric or
paper.
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