course was not appreciably diverted.

Then we got above these currents, and remained at our maximum level,
while we floated, still at only a moderate speed, the length of a
county. The descent then began, and once again, while we dropped
through the same disturbed region, the same far-reaching and obtrusive
cross-current assailed us. It was quite obvious that the vehement
currents were too slender to tell largely upon the huge surface of the
balloon, as it was being swept steadily onwards by the main wind, which
never varied in direction from ground levels up to the greatest height
attained.

This experience is but confirmation of the story of the wind told by the
wind gauges on the Forth Bridge. Here the maximum pressure measured on
the large gauge of 300 square feet is commonly considerably less than
that on the smaller gauge, suggesting that the latter must be due to
threads of air of limited area and high velocity.

Further and very valuable light is thrown on the peculiar ways of
the wind, now being considered, by Professor Langley in the special
researches of his to which reference has already been made. This
eminent observer and mathematician, suspecting that the old-fashioned
instruments, which only told what the wind had been doing every hour,
or at best every minute, gave but a most imperfect record, constructed
delicate gauges, which would respond to every impulse and give readings
from second to second.

In this way he established the fact that the wind, far from being a
body of even approximate uniformity, is under most ordinary conditions
irregular almost beyond conception. Further, that the greater the speed
the greater the fluctuations, so that a high wind has to be regarded as
"air moving in a tumultuous mass," the velocity at one moment perhaps
forty miles an hour, then diminishing to an almost instantaneous calm,
and then resuming. "In fact, in the very nature of the case, wind is not
the result of one simple cause, but of an infinite number of impulses
and changes, perhaps long passed, which are preserved in it, and which
die only slowly away."

When we come to take observations of temperature we find the conditions
in the atmosphere above us to be at first sight not a little complex,
and altogether different in day and night hours. From observations
already recorded in this volume--notably those of Gay Lussac, Welsh, and
Glaisher--it has been made to appear that, in ascending into the sky in