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Again, in order to utterly destroy all germs M. Pouchet
produced water from the combustion of hydrogen in air;
but even in this water he found organisms. Had he seen,
however, as you have, the manner in which the air is clouded
with floating matter, would he have concluded that the
deportment of water which had been permitted to trickle
through such air could have the least influence in deciding
this great question ? I think not. Here is a quantity of
water produced and collected by allowing a hydrogen-flame
to play upon the polished bottom of a silver basin, in which
ice had been placed. This water is clear in the common
light; but in the condensed electric beam it is seen to be
laden with particles, so thick-strewn and minute, as to pro-
duce a continuous cone of light. In passing through the
air the water loaded itself with this matter, and doubtless
became charged with incipient life.

Let me now draw your attention to another experiment
of Pasteur. He prepared twenty-one flasks, each contain-
ing a decoction of yeast, filtered and clear. He boiled the
decoction, so as to destroy whatever germs it might contain,
and while the space above the liquid was filled with pure
steam he sealed his flasks with a blow-pipe. He opened ten
of them in the deep, damp caves of the Paris Observatory,
and eleven of them in the court-yard of the establishment.
Of the former, one only showed signs of life subsequently.
In nine out of the ten flasks no organisms of any kind
were developed. In all the others organisms speedily ap-

Now here is an experiment conducted in Paris; let us
see whether we cannot throw light upon it in London. I
place this large flask in the beam, and you see the luminous
track crossing it from side to side. The flask is filled with
the air of this room, charged with its germs and its dust,
and hence capable of illumination. But here is another
similar flask, which cuts a clear gap out of the beam. It is

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