Provide a phial one-fourth filled with any coloured water, and with a
glass tube passing through the cork, or cemented into the neck of the
phial, so as to be air-tight; the tube may reach to within a quarter
of an inch of the bottom of the phial, so as to dip below the surface
of the liquid. Hold this little instrument before the fire, or plunge
it into hot water, when the air that is in the phial will expand, and
force up the coloured liquor into the tube.