im. By sheer genius Bacon had foreseen that the emptied
globe must be filled with SOMETHING, and for this something he suggests
"ethereal air" or "liquid fire," neither of which, we contend, were
empty terms. With Bacon's knowledge of experimental chemistry it is a
question, and a most interesting one, whether he had not in his mind
those two actual principles respectively of gas and air rarefied by heat
on which we launch our balloons into space to-day.

Early progress in any art or science is commonly intermittent. It was so
in the story of aeronautics. Advance was like that of the incoming tide,
throwing an occasional wave far in front of its rising flood. It was
a phenomenal wave that bore Roger Bacon and left his mark on the sand
where none other approached for centuries. In those centuries men were
either too priest-ridden to lend an ear to Science, or, like children,
followed only the Will-o'-the-Wisp floating above the quagmire which
held them fast. They ran after the stone that was to turn all to gold,
or the elixir that should conquer death, or the signs in the heavens
that should foretell their destinies; and the taint of this may be
traced even when the dark period that followed was clearing away. Four
hundred years after Roger's death, his illustrious namesake, Francis
Bacon, was formulating his Inductive Philosophy, and with complete
cock-sureness was teaching mankind all about everything. Let us look
at some of his utterances which may help to throw light on the way he
regarded the problem we are dealing with.

"It is reported," Francis Bacon writes, "that the Leucacians in ancient
time did use to precipitate a man from a high cliffe into the sea; tying
about him, with strings, at some distance, many great fowles; and fixing
unto his body divers feathers, spread, to breake the fall. Certainly
many birds of good wing (as Kites and the like) would beare up a good
weight as they flie. And spreading of feathers, thin and close, and in
great breadth, will likewise beare up a great weight, being even laid
without tilting upon the sides. The further extension of this experiment
of flying may be thought upon."

To say the least, this is hardly mechanical. But let us next follow
the philosopher into the domain of Physics. Referring to a strange
assertion, that "salt water will dissolve salt put into it in less
time than fresh water will dissolve it," he is at once ready with an
explanation to fit the case. "The