nd admiration, which the complex trick work of
an elaborate vacuum tube does not excite in the least. It will be
noted that this method may, and often does, involve a preliminary
thickening of the glass.

With tubes over an inch in diameter I have no idea as to what is the
best mode of procedure--whether, for instance, a quantity of sand or
gas coke might not be used to stuff out the tube during bending, but
in this case there would be the difficulty of removing the fragments,
which would be sure to stick to the glass.

Of course, if the bend need not be short, the tube could be softened
in a tube furnace and bent in a kind of way. I must admit that with
tubes of even less than one inch in diameter I have generally managed
best by proceeding little by little. I heat as much of the glass as I
can by means of a gigantic blow-pipe, having a nozzle of about an inch
in diameter, and driven by a machine-blower.

When I find that, in spite of blowing, the tube begins to collapse, I
suspend operations, reheat the tube a little farther on, and so
proceed. If by any chance any reader knows a good laboratory method
of performing this operation, I hope he will communicate it to me.
After all, the difficulty chiefly arises from laboratory heating
appliances being as a rule too limited in scope for such work.

The bending of very thin tubes also is a difficulty. I have only
succeeded here by making very wide bends, but of course the blowing
method is quite applicable to this case, and the effect may be
obtained by welding in a rather thicker bit of tube, and drawing and
blowing it till it is of the necessary thinness. This is, however, a
mere evasion of the difficulty.

Sec. 36. Spiral Tubes.

These are easily made where good heating apparatus is available. As,
however, one constantly requires to bend tubes of about one-eighth
inch in diameter into spirals in order to make spring connections for
continuous glass apparatus, I will describe a method by which this is
easily done. Provide a bit of iron pipe about an inch and a quarter
in outside diameter. Cover this with a thick sheath of asbestos
cloth, and sew the edges with iron wire. Hammer the wire down so that
a good cylindrical surface is obtained. Make two wooden plugs for the
ends of the iron pipe. Bore one to fit a nail, which may be held in a
small retort clip, and fasten a stout wire crank handle into the other
one. Support the neck of the handle by means