ce echoed, into which the light penetrated discreetly through stained
glass windows set in ribs and rosettes of stone. At the back were huge
raised benches, with room for an audience of many hundreds; at the other
end, where the choir once was, stood an enormous chimney mantel; in the
middle was a large, massive table, corroded by the chemicals. At one end
of this table was a tarred tub, lined inside with lead and filled with
water. This, I at once learned, was the pneumatic trough, the vessel in
which the gases were collected.

The professor begins the experiment. He takes a sort of large, long
glass bulb, bent abruptly in the region of the neck. This, he informs
us, is a retort. He pours into it, from a screw of paper, some black
stuff that looks like powdered charcoal. This is manganese dioxide,
the master tells us. It contains in abundance, in a condensed state
and retained by combination with the metal, the gas which we propose to
obtain. An oily looking liquid, sulfuric acid, an excessively powerful
agent, will set it at liberty. Thus filled, the retort is placed on a
lighted stove. A glass tube brings it into communication with a bell jar
full of water on the shelf of the pneumatic trough. Those are all the
preparations. What will be the result? We must wait for the action of
heat.

My fellow pupils gather eagerly round the apparatus, cannot come close
enough to it. Some of them play the part of the fly on the wheel and
glory in contributing to the success of the experiment. They straighten
the retort, which is leaning to one side; they blow with their mouths on
the coals in the stove. I do not care for these familiarities with the
unknown. The good natured master raises no objection; but I have never
been able to endure the thronging of a crowd of gapers, who are very
busy with their elbows and force their way to the front row to see
whatever is happening, even though it be merely a couple of mongrels
fighting. Let us withdraw and leave these officious ones to themselves.
There is so much to see here, while the oxygen is being prepared. Let
us make the most of the occasion and take a look round the chemist's
arsenal.

Under the spacious chimney mantel is a collection of queer stoves, bound
round with bands of sheet iron. There are long and short ones, high
and low ones, all pierced with little windows that are closed with
a terracotta shutter. This one, a sort of little tower, is formed of
several parts place