k; the flame
is scarcely visible in a bright light, and the heat given by either the
ordinary flame or the blowpipe flame produced from alcohol is
considerably less than that from a similar flame in which coal gas is
used. For small work, however, the facility with which a spirit lamp may
be lighted may more than counterbalance these disadvantages at times.

_Paraffin Wax._--Where there is no coal gas available and the blowpipe
is only required at intervals, and especially where high portability is
required, there are few fuels so convenient as paraffin wax. This may be
obtained in pieces of a satisfactory size by cutting paraffin candles,
from which the wick has been withdrawn, into lengths of about half an
inch. These cut pieces have the advantage over any oily fuel, such as
colza oil, that they can be wrapped in paper or carried in a cardboard
box; further they will keep indefinitely, even in the presence of air,
without undergoing any perceptible change.

_Forms of Lamp for Paraffin Wax._--Probably, the best form is that
devised by Thomas Bolas, and described by him in the _Journal of the
Society of Arts_, December 2nd, 1898. This lamp consists of a small open
tray of iron, through which pass three or more flat tubes, and between
these tubes are placed small flat pieces of wick, the fit being such
that the pieces of wick may be adjusted easily by means of a pair of
pointed tweezers.

The flame thus obtained, instead of having one large hollow, is broken
or divided so that the combustion is concentrated into a smaller area,
and the air blast, which is directed across the flame, carries the flame
with it in a more complete manner than is the case with the ordinary
flame; a more thorough combustion being realised by this arrangement.

Another advantage is the ease with which the wick may be changed and a
larger or smaller wick inserted to suit the flame to any size of air
jet.

This form of lamp may be used for oily fuel, although it is specially
suitable for paraffin wax.

Two small pieces of bent tin-plate may be used as side covers, and these
serve to adjust the flame within certain limits. A tin-plate cover which
fits easily over the whole lamp serves as an extinguisher. The complete
lamp is shown by _d_, Fig. 16, and this figure shows also a quick-change
air-jet device, the whole arrangement forming a blowpipe for use where a
non-gaseous fuel is to be employed.

Although the lamp just described is desirabl