may be particularly
convenient.[9]

[Footnote 9: Professor Soddy, in a paper read before the Royal Society
on the 15th November 1906, warns experimenters against vacua created
by charcoal cooled in liquid air (the method referred-to in the text),
unless as much of the air as possible is first removed with a pump and
replaced by some argon-free gas. According to him, neither helium nor
argon is absorbed by charcoal. By the use of electrically-heated
calcium, he claims to have produced an almost perfect vacuum.--ED.]

Thanks to these studies, a considerable field has been opened up for
biological research, but in this, which is not our subject, I shall
notice one point only. It has been proved that vital germs--bacteria,
for example--may be kept for seven days at -190 deg.C. without their
vitality being modified. Phosphorescent organisms cease, it is true,
to shine at the temperature of liquid air, but this fact is simply due
to the oxidations and other chemical reactions which keep up the
phosphorescence being then suspended, for phosphorescent activity
reappears so soon as the temperature is again sufficiently raised. An
important conclusion has been drawn from these experiments which
affects cosmogonical theories: since the cold of space could not kill
the germs of life, it is in no way absurd to suppose that, under
proper conditions, a germ may be transmitted from one planet to
another.

Among the discoveries made with the new processes, the one which most
strikingly interested public attention is that of new gases in the
atmosphere. We know how Sir William Ramsay and Dr. Travers first
observed by means of the spectroscope the characteristics of the
_companions_ of argon in the least volatile part of the atmosphere.
Sir James Dewar on the one hand, and Sir William Ramsay on the other,
subsequently separated in addition to argon and helium, crypton,
xenon, and neon. The process employed consists essentially in first
solidifying the least volatile part of the air and then causing it to
evaporate with extreme slowness. A tube with electrodes enables the
spectrum of the gas in process of distillation to be observed. In this
manner, the spectra of the various gases may be seen following one
another in the inverse order of their volatility. All these gases are
monoatomic, like mercury; that is to say, they are in the most simple
state, they possess no internal molecular energy (unless it is that
which heat is capable o