saline substances, even fixed alkali, are volatilized in a
few seconds.

6. Gold, silver, and probably platina, are slowly volatilized without
any particular phenomenon.

7. All other metallic substances, except mercury, become oxydated,
though placed upon charcoal, and burn with different coloured flames,
and at last dissipate altogether.

8. The metallic oxyds likewise all burn with flames. This seems to form
a distinctive character for these substances, and even leads me to
believe, as was suspected by Bergman, that barytes is a metallic oxyd,
though we have not hitherto been able to obtain the metal in its pure or
reguline state.

9. Some of the precious stones, as rubies, are capable of being softened
and soldered together, without injuring their colour, or even
diminishing their weights. The hyacinth, tho' almost equally fixed with
the ruby, loses its colour very readily. The Saxon and Brasilian topaz,
and the Brasilian ruby, lose their colour very quickly, and lose about a
fifth of their weight, leaving a white earth, resembling white quartz,
or unglazed china. The emerald, chrysolite, and garnet, are almost
instantly melted into an opake and coloured glass.

10. The diamond presents a property peculiar to itself; it burns in the
same manner with combustible bodies, and is entirely dissipated.

There is yet another manner of employing oxygen gas for considerably
increasing the force of fire, by using it to blow a furnace. Mr Achard
first conceived this idea; but the process he employed, by which he
thought to dephlogisticate, as it is called, atmospheric air, or to
deprive it of azotic gas, is absolutely unsatisfactory. I propose to
construct a very simple furnace, for this purpose, of very refractory
earth, similar to the one represented Pl. XIII. Fig. 4. but smaller in
all its dimensions. It is to have two openings, as at E, through one of
which the nozle of a pair of bellows is to pass, by which the heat is to
be raised as high as possible with common air; after which, the stream
of common air from the bellows being suddenly stopt, oxygen gas is to be
admitted by a tube, at the other opening, communicating with a gazometer
having the pressure of four or five inches of water. I can in this
manner unite the oxygen gas from several gazometers, so as to make eight
or nine cubical feet of gas pass through the furnace; and in this way I
expect to produce a heat greatly more intense than any hitherto known.
T