the temperature did not
rise beyond a bright red heat.

The heap of fragments being found satisfactory, the next thing is to
fuse some of the pieces together. Unless the preliminary heating has
been efficiently carried out this will prove an annoying task, because
a rock crystal generally contains so much water that it splinters
under the blow-pipe in a very persistent manner. There are two ways
of assembling the fragments. One is to place two tiles or bricks on
edge about the heap of quartz lying upon a third tile, so that the
heap occupies the angular corner or nook formed by the tiles (Fig.
64).

The oxygas blow-pipe previously described is adjusted to give its
hottest flame, the bags being weighted by at least two hundredweight,
if of the size described (see Sec. 15).

The tip of the inner cone of the blow-pipe is brought to bear directly
upon one of the fragments, and if the operation is performed boldly it
will be found that the surface of the fragment can be fused, and the
fragment thus caused to hold together before the lower side gets hot
enough to suffer any contamination from the tile or brick. A second
fragment may be treated in the same way, and then a third, and so on.

Finally, the fragments may be fused together slightly at the corners,
and a stick may thus be formed. Of course a good deal of cracking and
splitting of the fragments takes place in the process; the best
pieces to operate upon are those which are well cracked to begin with,
and that in such a way that the little fragments are interlocked.

An alternative method which has some advantages is to arm a pair of
forceps with two stout platinum jaws, say an inch and a half long, and
flattened a little at the ends. The fragments are held in these
platinum forceps and the blow-pipe applied as before. This method
works very well in adding to a rod which has already been partly
formed, but the jaws require constant renewals. The first fragment
which is fused sufficiently to cohere may also be fused to a bit of
tobacco pipe, or hard glass tube or rod, and the quartz stick
gradually built up by fusing fresh pieces on to the one already in
position.

Fig. 64.

Since the glass or pipeclay will contaminate the quartz which has been
fused on to it, it is necessary to discard the end pieces at the close
of the operation. A string of fragments having been collected and
stuck together, the next step is to fuse them down into a uniform rod.