The Sun.
London, England, 1864-10-13 00:00:00

Forecasts of Weather.

The following memorandum, published for gene-
ral information by Vice-Admiral R. Filz-Roy,
pears in the Lifeboat, the journal of the National
Lifeboat loeitution

FORECASTS OF WEATHER.
Many persons have asked questions about forecasts of
weather and their principles. Some have impugned their
accuracy, and a few have demurred to their having any
claim to a really scientific basis. No doubt that as very
different views of atmospheric commotions or changes are
taken by able men, such subjec's may scarcely seem worth
their earnest attention, because as yet they have not been
brought to the verification of a rigid mathematical analysis.
But to metaphysical inquiries, and to other researches cr
avocations, indispensably useful, one might take objection,
and decline their study on similar grounds. Meteorology
physical facts, excessively useful as
n,t only abounds in
well as interesting, but it demands an extensive range of
intalectual and extremely comprehensive considerations.
One cannot Lk() it in`o full use without duo study; yet
who is there without an independent opinion of the
weather, and perhaps too little understood barometric indi-
cations ? Having ascertained that the principal atmos-
pheric currents are incessantly in more or less circuiteu=
but mutually opposed progress, sometimes side by side but
in contrary directions, sometimes superposed, one or other
being nearest the earth's surface, temporarily—and always
having lateral as well as direct progression, we have a clue
to their dynametry—by observations at distant stations and
by telegraphing to a centre, somewhat like that which
might be given in a tidal estuary to an observer at a fixed
station, by ships swinging in advance or receding tide-
streams. By the tension or barometric pressure, the
temperature and other characteristics of the air at
each eta' ion—by the approximate knowledge now possessed
of the set, turn, or progression of atmospheric currents—
of their relative breadth horizontally, and of the circui-
tous eddies usually, or often, between their edges or
boundaries—one may tell what conditions of air exist
within some hundred miles around—say a sweep of 500
miles from London (as a centre), and, which is of far more
value, what changes of movements are impending. The
capability of doing this for about two days in advance
rests on the proved fact of a general lateral translation
toward the east in the temperate z3r-e, while northerly,
southerly, or other (mixed) currents of air are in very
various movement, the practical results on the earth's
surface being usually composite motions. By
thus con-
sidering the atmospheric area above, around, and within
some hundred miles of us ; by statical observations at the
same hour, and by summary calculations of a dynamic
character, all the principal motions and changes are
brought within the grasp of forecast. But this applies
only to general and principal averages, not to local pecu-
liarities or special disturbances so limited in nature that they
do not affect more than a few score miles' expanse of atmos-
phere, It ought to be kept in mind that broad shallow
currents aro the chief aerial features, below or between or
among which there can be no vacancy, unless momentarily,
as when a violent blast of wind is caused by a sudden
(approximate) vacuum ; and that when currents act against
each other (gravity restraining upward motion) their ten-
dency is to cause more or less rotation. The lamented Espy
said that winds always set from the place of higher baro-
meter towards that of lower, but he also said (which some
writers seem to have overlooked) that the meeting of such
winds causes a circuitous effect. Espy's views accord with
those of the authoritative Dove and our illustrious Her-
schel. The word cyclone has been so associated with
storm that few persons attach to it now the simple and
ancient sense of circuit or circuitous. Without duly fol
lowing the progress and ultimate destination of materiel
fluid. air having great bulk, infinite elasticity, and more
or lossvis inertia, or rather momentum, according to me-
chanical laws, some persons have imagined that air cure
rents intermix, as if unresistingly, instead of opposing each
other for a time, especially if in rapid motion, just like cur-
rents of water in a river or in the sea. Air-streams in op-
position must deft pct or turn each other, or go upt;fard
(against gravitation). Without a general, lateral, or trans-
mer:dional movement, or translation of atmosphere toward
the east in the temperate zones, but westward in the inter-
tropical regions—in addition to meridional movements from
and toward the poles (of which full explanations are given
elsewhere), it would not be possible to forecast the character
of wind and weather beyond one day's interval. It is the
prescience of dynamic consequences arising out of statical
facts that enables a really scientific calculation of probabi-
lities to be made. certainty is not yet attainable; but a
fair average probability, for a certain area or district
is already within our reach. Oat of these forecasts
spring the cautionary notices of impending storms. It is by
a continuous observation of the changes and indications of
change that we are now enabled to decide and direct with
confidence. Without such a generally-informed state we
should often be surprised, as we should derive our warnings
solely from distant stations, and should not be able as now
frequently to warn even outposts, such as Nairn, Yalentia,
or Rochefort. That errors have occurred—that we have
been too slow, or have given warning where it seemed to
have been unnecessary—may appear to have been unavoid-
able in such new and tentative experiments. But there
have been four special causes of occasional failure which
ought to be fairly considered.
"I. A watch having been officially set to report on the
results of each cautionary signal, has somewhat discouraged
such speedy action as might otherwise have been taken in
signalling, lest a record of their inutility should be compiled
rather than the contrary. 2. Public offices are not open on
Sundays, and only a few principal telegraph stations are
then available. Hence there is sometimes unavoidable delay
between Saturday and Monday. 3, No one or two persons
can be always at their station all the year round from morn-
ing to night. The new subject of forecasting and warn-
ing is hardly yet so familiar to many persons, however
zealous, as it may be in dug time, Lastly, the telegraph
offices are not open in general till 8 or 9 in the morning, or
after those hours at night; therefore official communica-
tions are only practicable, over so wide a range as ours,
between those times of the day,"
To communicate between Nairn or Valentia or Rochefort
and our office in London usually takes about two hours, in
actual practice. For proofs of what has bean thus stated,
perhaps too dogmatically, about the movements of air-cur-
rents and their lateral translation, I would suggest a general
reference to various publications, except fpr one recent and
very remarkable instance. During the storm of October
29-30, such remarkable sudden and violent shifts of wind
took place about the same time at many places in a nearly
meridional direction across England, between or by Oxford,
Greenwich, Nottingham, and other places, that even to
meteorologists they seemed unaccountable—but if we con-
template parallel currents, side by side, moving rapidly in
opposite directions, and having also a lateral movement to
the eastward, such sudden and meridional changes may bee
come as easy to comprehend as those so well described by
aeronauts, who passed out of one stratum or current of air
into another, so closely superposed that while the balloon
was tilted (drageel aside as it were) by the one, the car
was affected differently by the other. This momentary
effect was accompanied by a rushing sound like that of a
torrent of water. These currents had different tempera-
tures, electric characters, degrees of dryness or moisture,
and horizontal motions. (The sound, caused by pressure
end friction, is suggestive of various ideas in connection
with heat and electric considerations, inadmissible here.)
In this ease, of course, the representative of an observatory
moved vertically through horizontal air-currents, at times
differing in velocity (referred to earth's surface) from some
30 to 60 miles an hour. In the former instance—that of
a land station—the currents ware separated vertically, their
division passing across any place suddenly but horizontally.
At the present time our meteorologic communications are
utilised, and highly appreciated on the continent. At about
ten in the morning (as seen as in London), Paris receives
notices of wind and weather from our most distant stations,
and distributes them. Near the same time we rsceive tele-
grams at this office from three French coast stations—B rest,
Two hours afterwards the French Government despatches
Lorient, and Rochefort—being all that we can utilise.
our forecasts, and (if any) cautionary notices to more than
eighteen stations on the coasts of France, This British
system has therefore incurred a large responsibility. What
does it cost ? is of course a frequent question, The Me-
teorologic-office of the Board of Trade, and for the Admiralty
likewise, was established in 1855, with a yearly estimate of
£4,200. This was for many duties, exclusive of those now
superadded, not then contemplated. To include and provide
for all—with these additional objects, and their contingent
expenses— I now ask to have £5,800, being only £1,600 more
than in 1855.58 when meteorologic investigations had nut
led to their practical utilisation nationally.
In conclusion,
may I be permitted to say that, while ad-
mofittatirndgy many errors
itror sof judgment and numerous instances
has been proved by general opinion of
the maritime, if not also of the agricultural, interests that
the system of meteorologic information existing now under
the Board of Trade is we rth I's cost to the nation, and is
deserving of efficient maintenance.—R. FeTz-R oes.
Posteript,—Having been asked to send out forecasts, and
occasional cautionary notices to the Midland districts, I am
anxious to say that such detailed definitions seem hardly
requsite, as they could not be given for highlands and
valleys, exposed districts, and sheltered places alike. Fair
comparisons of the daily weather reports or notices for
those coasts which are nearest to any such inland place--1
especially those to the westward—and due consideration of
the reports immediately preceding the time of observation,
or exligcte I, as probable to occur during next day, or on
that to follow it—may give better reformation than a speciel
forecast—not duly estimating local peculiarities. The whole
area of the British islands is so small, comparatively, that
changes over them may be better estimated comprehen-
sively, on a wide scale (having especial reference to princi-
pal upper, or cloud bearing currents), rather than to local
effects in confined or very limited districts,

CHURCH RATE CONTEST IN TTIE CITY.—The
parishioners of St. Katherine Creo Church, at the eastern
division of the City in and around Leadenhall-street, were
on Tuesday summoned to attend a poll which had been de-
manded at the vestry meeting held on the Thursday pre-
ceding, to decide whether a proposition then made for a
church rate of 10d in the pound should be carried or not
At the poll Churchwarden Nash presided, and at the close
ho announced the number of voles iocorded to be—for the
rate, 5S ; against it, 47. The church rate of 104 was
accordingly declared to be carried.