tain scientific facts and memoranda collected by the talented French
aeronaut whom we are following are too interesting to be omitted. In the
same journey to which we have just referred the voyagers, when nearly
over Calais, were witnesses from their commanding standpoint of a very
striking phenomenon of mirage. Looking in the direction of England, the
far coast line was hidden by an immense veil of leaden-coloured cloud,
and, following this cloud wall upward to detect where it terminated, the
travellers saw above it a greenish layer like that of the surface of
the sea, on which was detected a little black point suggesting a walnut
shell. Fixing their eyes on this black spot, they presently discerned
it to be a ship sailing upside down upon an aerial ocean. Soon after, a
steamer blowing smoke, and then other vessels, added themselves to the
illusory spectacle.

Another wonder detected, equally striking though less uncommon, was
of an acoustical nature, the locality this time being over Paris. The
height of the balloon at this moment was not great, and, moreover,
was diminishing as it settled down. Suddenly there broke in upon the
voyagers a sound as of a confused kind of murmur. It was not unlike
the distant breaking of waves against a sandy coast, and scarcely less
monotonous. It was the noise of Paris that reached them, as soon as they
sank to within 2,600 feet of the ground, but it disappeared at once when
they threw out just sufficient ballast to rise above that altitude.

It might appear to many that so strange and sudden a shutting out of a
vast sound occurring abruptly in the free upper air must have been more
imaginary than real, yet the phenomenon is almost precisely similar to
one coming within the experience the writer, and vouched for by his son
and daughter, as also by Mr. Percival Spencer, all of whom were joint
observers at the time, the main point of difference in the two cases
being the fact that the "region of silence" was recorded by the French
observers as occurring at a somewhat lower level. In both cases there
is little doubt that the phenomenon can be referred to a stratum of
disturbed or non-homogeneous air, which may have been very far spread,
and which is capable of acting as a most opaque sound barrier.

Attention has often been called in these pages to the fact that the
action of the sun on an inflated balloon, even when the solar rays may
be partially obscured and only operative for a few p