nricher of coal gas, 5 per cent. of it would increase the
luminosity of 16-candle gas by about 40 per cent.

Oxygen has been obtained for some time past from the air on a
commercial scale by the Brin process, and at the present time there
seems every prospect of our being able to obtain oxygen at a rate of
about 3s. 6d. per 1,000 cubic feet. Another process by which this
important result can also be obtained was first introduced by Tessie
du Mothay, and has now just been revived. It consists of passing
alternate currents of steam and air over sodic manganate heated to
dull redness in an iron tube; the process has never been commercially
successful, for the reason that the contents of the tube fused, and
flowing over the surface of the iron rapidly destroyed the tubes or
retorts, and also as soon as fusion took place, the mass became so
dense that it had little or no action on the air passing over it. Now,
however, this difficulty has been partly overcome by so preparing the
manganate as to prevent fusion, and to keep it in a spongy state,
which gives very high results, and the substance being practically
everlasting, the cost of production is extremely low.

It is proposed to feed this by a separate system of pipes to small gas
jets, and by converting them into practically oxyhydrogen blow pipes,
to raise solid masses of refractory material to incandescence, and
also by supplying oxygen in the same way to oil lamps of particular
construction, to obtain a very great increase in illuminating power.

Whether these methods of employing cheap oxygen would be successful or
not, I do not wish to discuss at the present time, but there is no
doubt but that cheap oxygen would be an enormous boon to the gas
manager, as by mixing 0.8 per cent. of oxygen with his coal gas before
purification, he could not only utilize the method so successfully
introduced by Mr. Valon at Ramsgate, but could also increase the
illuminating value of his gas.

In speaking of the structure of flame, I pointed out that close to the
burner from which the gas giving the flame is issuing, a space exists
in which no combustion is going on--in other words, a flame is never
in contact with the rim of the burner. This is best seen when the gas
is turned low--with a batswing burner, for instance--turned so low
that only a small non-luminous flame is left, the space between burner
and flame will appear as great as the flame itself, while, if the gas
is mixed w