necessary for experiments of this kind consists of a
small table ABCD, Pl. XII. Fig. 15, with a hole F, through which passes
a tube of copper or silver, ending in a very small opening at G, and
capable of being opened or shut by the stop-cock H. This tube is
continued below the table at l m n o, and is connected with the
interior cavity of the gazometer. When we mean to operate, a hole of a
few lines deep must be made with a chizel in a piece of charcoal, into
which the substance to be treated is laid; the charcoal is set on fire
by means of a candle and blow-pipe, after which it is exposed to a
rapid stream of oxygen gas from the extremity G of the tube FG.

This manner of operating can only be used with such bodies as can be
placed, without inconvenience, in contact with charcoal, such as metals,
simple earths, &c. But, for bodies whose elements have affinity to
charcoal, and which are consequently decomposed by that substance, such
as sulphats, phosphats, and most of the neutral salts, metallic glasses,
enamels, &c. we must use a lamp, and make the stream of oxygen gas pass
through its flame. For this purpose, we use the elbowed blow-pipe ST,
instead of the bent one FG, employed with charcoal. The heat produced in
this second manner is by no means so intense as in the former way, and
is very difficultly made to melt platina. In this manner of operating
with the lamp, the substances are placed in cuppels of calcined bones,
or little cups of porcelain, or even in metallic dishes. If these last
are sufficiently large, they do not melt, because, metals being good
conductors of heat, the caloric spreads rapidly through the whole mass,
so that none of its parts are very much heated.

In the Memoirs of the Academy for 1782, p. 476. and for 1783, p. 573.
the series of experiments I have made with this apparatus may be seen at
large. The following are some of the principal results.

1. Rock cristal, or pure silicious earth, is infusible, but becomes
capable of being softened or fused when mixed with other substances.

2. Lime, magnesia, and barytes, are infusible, either when alone, or
when combined together; but, especially lime, they assist the fusion of
every other body.

3. Argill, or pure base of alum, is completely fusible _per se_ into a
very hard opake vitreous substance, which scratches glass like the
precious stones.

4. All the compound earths and stones are readily fused into a brownish
glass.

5. All the