ght for hours!"

If such is the case with you, reader, you may very rightly assume that
the burner is not properly adjusted, and so does not give the _right
kind of flame_.

In order to get the hottest possible flame, the quantity of gas and air
must be mixed in the right proportions. A common fault is that there is
too much gas allowed to flow through the nipple, compared with the
amount of air being drawn in at the air aperture, fig. 13. The result
is, we get a flame of great length, but one which is not at all suited
to our requirements; and instead of giving up its heat to the tube and
the asbestos lining of the chimney, a large amount of gas we are
presumably burning _in_ the chimney is not being burnt there at all,
for, on applying a light just above the chimney top, a quantity of this
gas we are wasting will be seen to burn with a flickering blue flame.

To put matters right, it is necessary to do one of two things--either
cut down the supply of gas or increase the air-supply. Providing the air
aperture is normal, _i.e._, the same size as it was originally, it is
better to adjust the _gas_, which may be done by tapping up the nipple
N, as indicated in the enlarged sketch, fig. 14, until just the right
amount of gas can flow.

As a rule, if there is too much air, the flame will burn with a loud
roaring noise, and is liable to fire back. The nipple should then be
opened out with a small reamer--the tang of a small file, ground to a
long taper point, makes an admirable tool for this purpose. Whether the
burner is of the ordinary bunsen type, or the ring or stove type, the
above remarks apply, as in every case the flow of gas is governed by the
size of the orifice through which it flows.

There is no need to use anything beyond a touch of oil when putting in a
new tube, in order to make a perfectly tight joint; white or red lead
are quite unnecessary, and are liable to make it a troublesome matter to
remove the tube on future occasions. Neither should undue force be
applied when putting in new tubes; it is liable to wear the thread in
the firing block, which results in a partial stoppage of the ignition
hole, as indicated in fig. 15. This is especially the case if we happen
to get hold of a tube with its screwed part slightly smaller than usual.

The asbestos with which the chimney is lined should be about 1/8 in.
thick, and, when renewing, the same thickness should be used as
originally. A thicker board will r