e when complete control over
the size of the flame is necessary, and if the ideal conditions and
maximum heat are to be obtained, yet a simpler form of lamp will be
found to give very good results. Such a lamp may consist of a flat tin
tray, having a diameter of about three and a half inches and a depth of
about one inch. In this tray is a tin support for the wick, and the wick
itself may consist of a bundle of soft cotton, for example, a loosely
rolled piece of cotton cloth, but in either case the top of the wick
should be cut to approximately the same angle as that at which the
blowpipe jet meets the flame.

In using paraffin wax as a fuel, it is necessary to see that sufficient
wax reaches the wick to prevent charring during the first few minutes
before the bulk of the wax is melted.

_Animal and Vegetable Oils._--Almost any oil may be used as a fuel, but
many tend to become hard and gummy if allowed to stand in the air for
any considerable time. When this happens, the wick becomes clogged and
it is impossible to obtain a good flame. A number of the oils tend,
also, to produce rather strongly smelling smoke.

_A Flame-Guard for Use With Non-Gaseous Fuels._--In order to avoid the
eye-strain produced by the luminous base of the flame from a wick
burning paraffin wax or oil, it is often advantageous to make a small
tunnel of tin-plate, which can be rested on the sides of the lamp and
rises over the top of the wick. Such a flame guard is shown by _e_, Fig.
16.

_Small Rods and Tubes from Glass Scrap_:--It is scarcely practicable to
make small quantities of good glass with the blowpipe flame as the only
source of heat, but it is less difficult to make small rods or tubes
from glass scrap, and the ability to do this is sometimes of
considerable value when a small tube has to be joined on to some special
piece of apparatus made of glass of unknown composition. It may be
possible to obtain some fragments of similar glass, either from a broken
part of the apparatus or from a similar piece, and from these fragments
small tubes or rods can be made.

The fragments of glass may be melted together on the end of a clay
pipe-stem, care being taken to avoid trapping air bubbles as fresh
fragments are added to the molten mass. When a sufficient quantity of
glass has been accumulated, the viscous mass may be drawn out into a rod
by bringing another pipe-stem into contact with the hot mass, rotating
both pipe-stems steadily, and s