, 1891-11-04

every one the drops again poured down, till
at last the clouds were entirely expended"
In these quotations is given all is es-
sential in the newspaper reports now before
us. Although deficient in many details that
it would be desirable to know, they are
written by one who witnessed what he des-
cribed, and there seems no reason whatever
to doubt their genuineness and good faith,
we may therefore discuss the information
they afford, without misgivings of it's sub
stantial trustwOrthiDess.
1t is not antecedeutly improbable that,
in certain states OF the atmosphere, the
liberation of a large amount of heated gas
consisting wholly or in great part Of water
vap0ur, at an elevation where as rial move
ments are but little retarded by terrestrial
friction, may suffice to generate an ascend
ing cure Mt, and elementary physical con-
S~ideratiOns teach us that a mass of air
that would be called relatively dry at the
lower level, will in ascending speedily be-
come saturated and cOndense its surplus
vapour first as cloud, and eventually ~as..rain,
not indeed by acquiring more vap0ur, but
in virtue Of dynamic cOUling as it progress
sively expands under the diminished pres
sure of greater altit I'd es. But unless the
atmospheric strata thus Immediately affect
ed be already in a condition of unstable
eOuillbri UNI, unless the vertical decrease of
temperature in these strata is already some
what greater than the adiabatic rate of de-
crement, so that the ascending movement
once started can be maintained by the store
of energy already present in the form
of sensible temperature and the latent
heat of the included vapOur, the effect must
OfnecesSity be temporary and lOcal-mOre
of the nature of a small thunder storm, or
cloud burst, than of the widely extended or
4 II.
metric depression.
In fact the possibility of rainfall prOduc-
ton depends ON the possibility Of producing
and maintaining an upward movement i'll
the atmosphere. There is always some va
pour present in the air, generally sufficient
to form clouds when dynamically cooled by
an ascent through two or three thousand
feet although such air, while resting on the
ground and warmed by It's contact, may be
verydry as Judged by our feelings and by
the evidence of the hygrOmeter. The amount
of energy yielded by any moderate provi-
sion of OxyhydrOgen balloons and dynamite
is but infnitesimal in comparison with that
all eady locked up in the atmosphere and
it's vapOur, and which, under the clrcum-
stances above specified, viz a vertical de-
crease of temperature exceeding a certain
fixed rate, is available for maintaining a
movement OHC0ScG up dAU ChO P"tC Pl"SOU
by the heated gases of such experiments as
those now described can be little more than
that of a trigger that releases a detent.
1t seems highly probable that on August
18th the atmosphere was in this unstable
condition. Even in the warm stratum
resting on the ground, the humidity was 60
per cent, of saturatiOn, clouds Gndicat
ing saturatiOn) existed at some height. and
rain began to fall almost Immediately, on
the conclusion of the explosions. 1t may be
noticed. too thai the time of day was that
at which the barometer is lowest at the
humidity, highest in the cloud forming
stratum, although in fine weather, lowest at
the ground surface. In the absence, then,
of any observations of the temperature and
humidity of the strata primarily stirred up
by the exploding balloons and dynamite,
seems likely that they were in a condition to
maintain ascending currents once started,
and even to communicate the disturbance
to regions around.
On the 26th the atmosphere was evident-
lv in a much more inert condition, and four
hours elapsed before rain fell, the dlstur-
bance being then apparently more local, and
of the nature ola thunderstorm However,
with the meagre data as yet before us, 1t
would be premature to attempt any critical
discussion of the processes in operation.
It is needless to say that popular theorizing
on this as on most other physical phenomena,