the peculiarities in the behaviour of each of them
before the blow-pipe, which is followed by a tolerably minute
description of the method of performing each of the fundamental
operations employed in fashioning glass apparatus. These are not very
numerous, and they should be thoroughly mastered in succession,
preferably upon tubes of both soda and lead glass. Then follows, in
Chapter IV., an account of the application of these operations to
setting up complete apparatus, full explanations of the construction of
two or three typical pieces of apparatus being given as examples, and
also descriptions of the modes of making various pieces of apparatus
which in each case present one or more special difficulties in their
construction; together with an account, which, I think, will be found
valuable, of some apparatus that has been introduced, chiefly during
recent years, for experimenting upon gases under reduced pressure,
_e.g._ vacuum taps and joints. Finally, in Chapter V., there is a short
account of the methods of graduating and calibrating glass apparatus for
use in quantitative experiments.

=The Working-place.=--The blow-pipe must be placed in a position
perfectly free from draughts. It should not face a window, nor be in
too strong a light, if that can be avoided, for a strong light will
render the non-luminous flames, which are used in glass-blowing, almost
invisible, and seriously inconvenience the operator, who cannot apply
the various parts of the flames to his glass with the degree of
certainty that is necessary; neither can he perceive the condition of
the glass so correctly in a strong light, for though in many operations
the glass-worker is guided by feeling rather than by seeing, yet sight
plays a very important part in his proceedings.

My own blow-pipe is placed near a window glazed with opaque glass, which
looks southwards, but is faced by buildings at a short distance. In dull
weather the light obtained is good; but on most days I find it
advantageous to shade the lower half of the window with a green baize
screen. Some glass-blowers prefer gaslight to daylight.

The form of the table used is unimportant, provided that it is of a
convenient height, and allows free play to the foot which works the
blower underneath it. The blower should be _fixed_ in a convenient
position, or it will get out of control at critical moments. The table,
or that part of it which surrounds the blow-pipe, should be covered