combinations, rather than by means of the balloon; and though, as
before remarked, the experiments of M. Pétin and others may probably
not be without useful results, we dismiss these brilliant
phantasmagoria with the charitable reflection, that the extravagance
of overweening hopefulness is, at least in an age which has witnessed
the advent of steam and electricity, more natural and more pardonable
than the scepticism of confirmed despondency; and that "he who shoots
at the stars," though missing his aim, will at all events shoot higher
than he who aims at the mud beneath his feet.

'Meantime, the science of meteorology--a subject intimately connected
with that of aëro-locomotion--though yet in its infancy, already
furnishes many indications of great importance, as establishing a very
strong presumption in favour of the existence of permanent atmospheric
currents, blowing continuously in various directions at different
degrees of elevation.

'We know that air, when rarefied by heat, becomes lighter and rises,
cold air immediately rushing in to supply its place; and it is
evident, therefore, that if two neighbouring regions of the atmosphere
are unequally heated, this inequality of temperature will give rise to
two currents of air--a warm one, in the upper region of the
atmosphere, blowing from the warmer to the colder region; and a cold
one, near the surface of the earth, blowing from the colder to the
warmer region. It can, therefore, hardly be matter of doubt, that
great permanent currents, caused by the unequal heating of the
equatorial and polar regions, do exist in the higher strata of the
atmosphere--an inference which is supported not only by the occurrence
of the trade-winds and the monsoon, but by a variety of other facts
and observations.