be shortly afforded by a memorable voyage
accomplished during the partnership of Messrs. Glaisher and Coxwell, one
which would certainly have found the travellers in far less jeopardy
had their car been convertible into a boat. We have already seen how
essential Wise considered this expedient in his own bolder schemes,
and it may further be mentioned here that modern air ships have been
designed with the intention of making the water a perfectly safe
landing.

The ballooning exploits which, however, we have now to recount had quite
another and more special object consistently in view--that of scientific
investigation; and we would here premise that the proper appreciation of
these investigations will depend on a due understanding of the attendant
circumstances, as also of the constant characteristic behaviour of
balloons, whether despatched for mere travel or research.

First let us regard the actual path of a balloon in space when being
manoeuvred in the way we read of in Mr. Glaisher's own accounts. This
part is in most cases approximately indicated in that most attractive
volume of his entitled, "Travels in the Air," by diagrams giving a
sectional presentment of his more important voyages; but a little
commonplace consideration may take the place of diagrams.

It has been common to assert that a balloon poised in space is the most
delicate balance conceivable. Its intrinsic weight must be exactly equal
to the weight of the air it displaces, and since the density of the
air decreases according to a fixed law, amounting, approximately, to
a difference in barometric reading of 0.1 inch for every 90 feet, it
follows, theoretically, that if a balloon is poised at 1,000 feet above
sea level, then it would not be in equilibrium at any other height, so
long as its weight and volume remain the same. If it were 50 feet higher
it must commence descending, and, if lower, then it must ascend till it
reaches its true level; and, more than that, in the event of either such
excursion mere impetus would carry it beyond this level, about which it
would oscillate for a short time, after the manner of the pendulum. This
is substantially true, but it must be taken in connection with other
facts which have a far greater influence on a balloon's position or
motion.

For instance, in the volume just referred to it is stated by M. Gaston
Tissandier that on one occasion when aloft he threw overboard a chicken
bone, and, immediately consul