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ENCYCLOPÆDIA METROPOLITANA;

OR,

UNIVERSAL DICTIONARY OF KNOWLEDGE.

Second Division.

ME TE OROLOG Y.

INTRODUCTORY OBSERVATIONS.

ton of

Irace the

Helegt. (1.) The condition of Man is so intimately connected on the verdant shores of Britain; all these, and a

Meteorology. with the various phenomena of the atmosphere, that he thousand more complicated inquiries, beset the investi

ology wa may, without impropriety, be regarded as a Meteorolo- gator at the very threshold of Meteorology, stimuIatroduce gist by nature. In all the varied circumstances of his lating him to ardent investigation, and inspiring him lory obserstate, whether as

a wild and uncultivated savage, ex- with wholesome caution. rations,

posed to the fury and inclemency of the weather, or in (3.) Meteorology, therefore, is not an insulated de- Connected the first stages of his civilization, when he has discovered partment of knowledge, detached from every other, but with many some feeble means by which he can shelter himself from is intimately related to many of its most important of the most the descending torrent and the scorching energy of the branches. With Chemistry, for example, it stands con- branches of sun; or when, as a shepherd and agriculturist, his in- nected in a highly interesting manner, and is blended knowledge.

terest leads him to watch with more anxiety the varying with almost every page of its splendid History. The Latinate ene tetion aspect of the sky, or as a mariner to connect the agita- Chemical constitution of the atmosphere, must at all with Chec Meteor. tions of the ocean with the terrible force of the sweep- times have been an interesting object of research ; and mistry. dogy with ing wind, he finds much of his happiness, and, at times, in later days, when this beautiful branch of inquiry le condieven his safety and existence, identified with the mighty has assumed so perfect a form, and unravelled so many

and changeful character of the great fluid ocean, in of the hidden mysteries of Nature, its relations to

which it has pleased the Almighty to place him. Meteorology have been contemplated with redoubled Dicult to

(2.) It would be difficult to trace the probable steps by interest. With the properties of Heat, and with the Heat:

which Man, during a long succession of Ages, has arrived distribution of temperature over the varied and unequal Seps of its at his present limited knowledge of atmospherical pheno- surface of the globe, Meteorology necessarily holds an inazly His. mena. The great causes which impeded the general timate connection. The principles are singularly curious fery, march of Physical Science, necessarily exercised their in- which mark the gradations of climate, and disclose the Gradations

fluence on this branch as on others; and when we consider interesting system of changes by which the atmospheric of climate.
the peculiarly intricate conditions connected with every currents are produced ; and a fertile and instructive
atmospherical problem ; the large advances that must branch of inquiry is opened by tracing, amidst the ap-
be made in many capital portions of knowledge, before parent uncertainty which characterises these diversified

one successful step can be made in this ; the subtile operations, something like the existence of laws; and
Causes
Ehich bare

nature of the medium which is the subject of investi- by endeavouring to embudy, in general analytical forms, retarded its gation; its singular relations to moisture; the changes representative values for them. It is thus that the adrasce.

it undergoes with every alteration of temperature; in Meteorologist has been enabled to obtain at the level of
one region influenced by the full power of a vertical the sea, an approximative value of the temperature of
sun, and in another chilled by the frozen masses of the his place of observation; and it is some evidence that
Polar zones; altering its circumstances on lofty hills, a few successful steps, at least, have been made in the
and again assuming new conditions in valleys ; the inquiry, when the mean temperature of a place can
islands of the West receiving the air that a few hours thus be obtained, sometimes within the fraction of a Gradations
before lingered over the countries of the East; the warm degree. Connected also with the same inquiry, is the of temper-
breath of the South softening the rigours of the colder consideration of the laws which mark the gradations ascend
regions of the North; the vapour rising from the of temperature, as we ascend above the Earth. There above the
bosom of the Atlantic, dropping richness and fertility are approximative laws which the ingenuity of the Earth.

VOL. V.

B

zone.

the
ate zone.

Meteor- Scientific Meteorologist has reached, which connect existing on the surface of the globe; determining the Meteorology. the temperature of the loftier regions of the air with altitudes of the loftiest mountains, fixing the elevations

ology. that of strata more accessible to Man; and in following of the sources of rivers, and of the positions of cities up the gradual system of changes which mark the de- which the enterprise of Man has reared, in many situa

crements of Heat, to the point at which water con. tions far above the level of the sea; and making Plane of geals, he has been enabled to fix in every latitude the known, in all its minutest forms, the exact conditions perpetual limits of perpetual frost in the air ; tracing it to its of the terrestrial surface, an interest of the most imfrost.

greatest point of elevation between the tropics, follow- portant kind is given to this application of the re-
ing it as it descends in the temperate regions, until it sources of Meteorology. The refinements, also, which Refinements

which have Vicissitudes sinks to its lowest possible level in the frigid zones. In have been introduced into Barometrical measurements,

been introof this great tracing also the varying altitudes of this magnificent by the employment of corrections; for the influ- duced into plane.

plane during the uncertain vicissitudes of the seasons ; ence of capillary attraction, and the accession of the Barometri-
marking its ascent during the tide of summer, and its minutest atoms of moisture; the varied shapes which cal measure-
descent when chilled by the blasts of winter; its the ingenuity of the analyst has given to the for- ments,
Northern portion rising, when by the increments of the mulæ of computation, all impart deep interest to this
solar declination the temperature of Europe and Asia important branch of Meteorology.

But it is from Atmosphe-
are augmented; or its Southern portion falling, as cor- the delicate and uniform changes which the atmo- ric tides.
responding regions of the globe lose a part of the sun's spheric tides display, that the Barometer becomes
vivifying power,—the subject has become connected with most important. In the torrid zone, these remark- Their re-
many other departments of the Natural Sciences, with able oscillations are disclosed with such admirable markable
the Geographical distribution of plants, for example, uniformity, that the Meteorologist contemplates the

uniformity

in the torrid and has given to Meteorology another claim to high and horary changes of the mercurial column, with a part of attentive consideration.

the certainty which marks the anticipations of the Radiant

(4.) With all the inquiries connected with radiant Heat, Astronomer. And even in the more varying regions of DiscoverHeai. the subject of Meteorology is also most intimately con- the temperate zone, where the changes from

heat to cold able also in nected. The atmosphere is influenced in different forms are most capricious, and where the winds, ever chang

temperby the innumerable objects of the material world, eaching, seem to impress the character of perpetual uncerhaving a radiating power of its own, and all exercising tainty on every thing connected with the Barometer, the

an influence on the air. To trace in their fullest Meteorologist has been enabled to detect an analogous
Solar radia- extent all the conditions connected with solar radiation, system of changes.
tion.

it became necessary for the Meteorologist to measure (6.) The state in which aqueous vapour exists in the Various re-
its effects in different latitudes; to follow its changing atmosphere is also another important branch of Meteor- lations of
influence through the different months of the year; ology, and has been the object of much anxious in- aqueous
to estimate its progress during the several hours of quiry. It is connected with all the interesting relations Vapour to

Meteorology the day; to trace its power on the varied tribes of of the Hygrometer; with the series of laws regulating

vegetation; and to discover, under all its diversified the force, the weight, and the expansion of vapour; the Terrestrial circumstances, its maximum force. In like manner, in discovery of the term at which precipitation takes place radiation. order to trace the laws which regulate terrestrial radia- from an alteration of temperature ; the rate of evapora

tion, the Meteorologist has found the extent of its power tion under different temperatures and with different
in different latitudes; compared its influence upon plains velocities of the wind; the consideration of the altera-
and mountains, and measured its effects in the several tion of volume which air undergoes from Heat, and from
months. All these inquiries have much extended the the accession of vapour; its alterations of density, and
labours of the Meteorologist, and opened to him most the changes of its Specific Gravity in different states of
fertile and instructive fields.

saturation. Density of (5.) While, by the agency of the Thermometer, these (7.) The subject of dew likewise unfolds to the in- Dew, the air. interesting phenomena bave been disclosed, the Baro- quiring Meteorologist very interesting properties. No

meter has unfolded the most singular relations respecting other investigation developes in a more perfect man

the density of the air. The early cultivators of Meteor. ner the singular relations of radiant Heat, and the Incessant ology must have almost despaired of being able to trace laws by which caloric is communicated from one body fluctuations, any thing like uniformity, amidst the incessant fluctua- to another. The vegetable world in particular opens a

tions which the Barometer displayed. Influenced, ap- fertile and most interesting train of observation. Of the
parently, by a multitude of capricious causes, it must different grasses, each draws from the atinosphere during
have seenied as if no clue existed by which any the night a supply of dew to recruit its energies, de-
resemblance to a law could be detected; yet later pendent on its form and its peculiar radiating power.
observers, employing instruments of a more perfect Every flower has a force of radiation of its own, sub-
construction, and extending their observations over a ject to changes during the day and the night; and the
longer period of time, have arrived at many important deposition of moisture on it is regulated by the peculiar
conclusions of the greatest interest to Meteorology, and law which this radiating power obeys; and this power
to the Physical Sciences in general. One of the most will itself be influenced by the aspect which the flower
useful of these, is that equality of pressure which the presents to the sky, unfolding to the contemplative mind
mean altitude of the Barometer, at the level of the sea, the most beautiful examples of creative wisdom.

has in every latitude disclosed, and which, as a standard (8.) With the phenomena of rain, its primary forma- Rain, hail, Applica

in so many interesting Physical investigations, is of tion, and the principles which regulate its descent; the snow. tions of the very great importance. In the applications of this formation of hail, the consideration of the laws that Barometer instrument, also, to many important objects connected occasionally impart to it its beautiful crystalline forms; to Physical with Physical Geography; in making us better ac. the still more delicate creation of snow, and the inGeography. quainted, for example, with the varied irregularities vestigation of the endless groups to which particular

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Metear conditions of temperature, and the peculiar circum- is a sign to the inhabitants of St. Kilda, that the West Meteorolasy, stances attendant on the vapour actually existing in wind is very distant from them.

ology. the air give birth, it is needless to say how closely (13.) With the most exalted branch of Physical

Meteorology Meteorology is connected.

knowledge, Astronomy, the Science of Meteorology useful in Cloods,

(9.) The formation and classification of clouds, the stands in many interesting relations. In determining Practical

varied and incessant changes which they present; the the exact situation of a celestial object, the conditions Astronomy. CorCox, &c. laws which regulate their suspension, and their gradual of the internal and external temperatures require con

and sometimes sudden destruction by rain, belong all stant observation ; nor must the movements of the
to this branch of Meteorological inquiry. So also the Barometer be neglected, when the delicate problem of
consideration of the laws which appear to influence the the Astronomical refractions is to be applied. Meteor-
formation of haloes, coronæ, parhelia, &c. all of whichology has indeed furnished to the latter many of its
owe their origin to the presence of aqueous particles most important elements.
existing in the air, place Meteorology in a most interest- (14.) In the inquiries also connected with the figure Figure and
ing relation to Light.

and extent of the atmosphere, the most beautiful appli- extent of the Electrical (10.) With all the phenomena of Electricity, the cations of the law of gravitation have been made. The atmosphere. phenomena. Meteorologist has claimed an intimate connection, ever Mathematician, in considering the figures of the atmo

since Franklin identified lightning with the ordinary spheres of the Planets, is necessarily led, in a peculiar
electric fluid. The first conception of the thunder rod, degree, to notice the volume of air surrounding the
was one replete with magnificence. To draw down sphere which he inhabits. Its spheroidal form has called
silently from a cloud the matter, which, if discharged, into action the most profound theories of analysis; and
would hurl destruction upon thousands, and destroy the the Meteorologist rejoices to find, that the great laws
finest monuments of Art, is an operation which seems to which Newton delivered respecting the system of the

impart to the feeble hand of Man, a portion of the power World, meet with some of their most interesting appliAurora

of the Supreme. The beautiful phenomena of the Aurora cations in that atmosphere, whose incessant mutations Borealis . Borealis, illuminating by their splendour those unex- it is his constant object to watch and record.

plored regions of Nature, which are covered at all times (15.) In this rapid sketch of the relations of Meteor- These difwith a hoary desolation ; their occasional descent into ology to some of the leading departments of Physical serent relathe temperate zones of the Earth; and the influence which Science, an attractive picture is exhibited of the im- tions of Metheir changeful coruscations is said to exercise in par- portance and value of the inquiry. The Meteorologist,

teorology ticular cases on the Magnetic needle, have identified in while he is engaged, either for his amusement or in- importance an especial manner the Science of Electricity with that striction, in tracing some of the steps of the great and value of Meteorology

system of atmospheric changes; in recording the in- of the inWinds. (11.) The general theory of winds, and their many cessant fluctuations of the Barometer, marking the quiry.

modifications, opens also another interesting and in- vicissitudes of temperature, or estimating the force and structive field of Meteorological inquiry. To trace influence of aqueous vapour, is thus preparing, somethe sources which produce those tremendous hurri- times unconsciously, materials for perfecting many of canes and storms, that spread desolation over the the other Sciences. While his primary object is, perfairest prospects of Nature, and which communicate haps, to arrive at some of the elements connected with likewise to the ocean its awful character and power; the great problem of climate, he is aiding the Astronoto consider the causes also of local winds; to account mer in forming his catalogues of the stars. The inquiry for the economy of Nature, in providing for the in- therefore is not only valuable in itself, but is rendered

habitants of the tropical regions the refreshing inter- doubly so by the relations which it bears to so many of Sea and changes of sea and land breezes ; and for the exist- the other Sciences. laza breezes ence of those periodical winds, which in some of the (16.) The condition of Meteorology at the present Present

regions of the Earth perform, for detinite periods, with moment is one of very great interest. Much has been condition of the most exact uniformity, their stated and particular attained, and much, very much, remains to be done. Meteorology courses ; facilitating the objects of navigation, and The chief wants appear to be improvement in the inimpressing a character of uniformity on the latitudes struments of observation, and unity amongst the obin which they abound; these, and many other inquiries servers. To copy the example of the most perfect of of an analogous kind, awaken in an uncommon degree the Physical Sciences, Astronomy, it may be remarked, the attention of the Meteorologist.

that that splendid department of knowledge has adNatural (12.) The cultivation of Meteorology is connected vanced to its present perfection, by the improvements

also, in an especial manner, with many of the depart that have been gradually imparted to its instruments ments of Natural History. With the habits of particular of observation, and to the cautious and accurate deducanimals it is intimately identified, the sagacious ob- tions that have been drawn from their successful emserver being enabled to anicipate many atmospheric ployment. In like manner must Meteorology advance, if changes from an attentive observation of them. The similar methods be adopted. It is true that the elements common Swallow has always been considered as connected with the inquiries of this Science are much weather-guide; and not only may the approach of more uncertain and variable; but an extension of the field rain be expected when she dips her wings in the of observation, both as regards space and time, must surstream, but even the gradations of climate may be mount many of them. The successive improvements marked by her approach. The voice of the solitary of the Telescope have revealed to the Astronomer unCrow, the clamours of the Pintado, and the activity of numbered clusters of stars; and the Micrometer, advance Ants, are all indications of coming rain ; and by the ing from year to year in improvement, has enabled him mariner, the approach of the stormy Peterel, seeking for to measure, with unhoped-for accuracy, the minutest shelter under the wake of his vessel, is regarded as the intervals of space. So must an improved construction harbinger of a storm. So that of the Fulmar to land, of the Barometer and other instruments employed in

History, ledications ci iginals.

а

Meteor. Meteorological observations, guided by a more cau

been gradual, from the less general to the more gene

Meteor ology.

tious spirit of induction, lead, in process of time, to ral laws of Nature; and it would be singular, indeed, if, vlogy.
like satisfactory results. When we reflect on the general in so complicated an inquiry as Meteorology, one
condition of Physical Science, at the time when Bacon which labours under so many disadvantages peculiar to
laid down the rules according to which Philosophical itself, a step should, all at once, be made to a single
inquiries ought to be prosecuted, and contrast it with principle comprehending all the particular phenomena
its condition now; how by the steady application of his which we know. The Meteorologist must be content,
inductive precepts many of its branches, which were like the cultivators of all the other departments of
characterised by uncertainty and doubt, have been re- Natural Science, to advance by careful induction ; to
duced to comparative certainty and order; it is not too interrogate Nature under all her forms, and not to aban-
much to expect, that Meteorology, although still sur- don the subject in despair, if her responses be not im-
rounded with so much difficulty and error, will here- mediate.
after attain its proper rank in the scale of the Sciences. (18.) There is one peculiarity, however, belonging Helps
The indefatigable recorder of atmospheric changes will to the Science of Meteorology, which distinguishes it in which
then no longer be classed with the mere empiric. A a particular degree from all the other Sciences; and Meteorology
survey of the past History of Physical knowledge will that is the helps it may receive from popular observa- may derive
lead us to consider this conviction as neither romantic tions of phenomena. Saussure has remarked,* that larobserva-
nor unnatural.

“it is humiliating to those who have been much occupied tions of Sources of error which (17.) The great error which the cultivator of Meteor- in cultivating the Science of Meteorology, to see an phenomena, the Meteor- ology has to avoid, is that tendency, which has more agriculturist or a waterman, who has neither instruologist has or less existed in different stages of its History, to a ments nor theory, foretell the future changes of the to avoid.

premature generalization departing from the narrow weather many days before they happen, with a preci

and cautious path which Bacon laid down. To sion, which the Philosopher, aided by all the resources His objects, accomplish an analysis of all the complicated phe- of Science, would be unable to attain." But there

nomena of the atınosphere into simple and original are no just grounds for the humiliation which the Swiss
principles, ought to be the aim and object of the Philo. Philosopher has here alluded to; for “the knowledge
sopher, and it is one well worthy of his lofty ambition of the Philosopher differs from that sagacity which
and hope. But to proceed with success, “it is neces-

directs uneducated men in the business of life, not in
sary to ascertain facts before we begin to reason, and kind, but in degree, and in the manner in which it is
to avoid generalizing in any instance, till we have com- acquired.”+ And when we consider, that the agricul-
pletely secured the ground which we have gained. Such turist and the waterman are always employed in the
a caution, which is necessary in all the Sciences, is, in open air, with their minds constantly occupied with an
a more peculiar manner, necessary here, where the object which interests them more immediately than it
very facts from which all our inferences must be drawn, does the Philosopher, it can be no matter of surprise

are to be ascertained only by the most patient atten- that they often group together facts, which, like the General

There is something specious and seductive in instinct of animals, serve to guide them in their theories

all attempts at generalization, and it seeins as if the predictions. The local sign which directs them may Exampies. specious and mind, from the influence of improper habits, rather be a fog which rises at a particular hour, in some

clung to the consideration of general principles, than peculiar locality, the appearance of a cloud on the
to those severe and rigorous modes of observation, summit of a mountain, to which their attention has
which the pure principles of the Inductive Logic re- been directed by many early associations, or the song
quire. But the History of knowledge is filled with or migration of certain birds. But if these limited
the most melancholy proofs of the absolute futility interpreters of Nature be transported to new seats, the
of all attempts of the kind; and notwithstanding the symbols which guided them in their own locality will
splendour and success that have resulted from the no longer be efficient ; and other trains of observation
application of the legitimate rules of Philosophy as must be begun, to fit them for their new condition. The
laid down by Bacon, we yet find a strong tendency views of the Philosopher are much more extended and
to violate them.

It seems

as if the mind delighted general. His aiın is not to limit his conclusions to a More gene. in hanging every thing on a single point, and adopt- single locality, but to develop them under their most ral views of

the Philoing some principle as an infallible rule, to make general form ; and it is then that the superiority of well

sopher. the whole framework of Nature bend to its dictates, directed observations becomes manifest. If, indeed, “It required nothing less," says an eminent Philoso- the Scientific Meteorologist could be constantly occupied pher, † “ than the united splendour of the discoveries like the agriculturist and the waterman, in watching brought to light by the new Chemical School, to tear the appearances of the heavens, our knowledge of atthe minds of men from the pursuit of a simple and mospheric phenomena would soon be prodigiously inprimary element ; a pursuit renewed in every Age with creased; but unable thus to employ himself, it will be an indefatigable perseverance, and always renewed in the object of the genuine cultivator of Meteorology to vain;" and the History of Meteorology is filled with draw from the experience of even uneducated men all like impotent attempts. But checked as its growth the helps he is able. has been by the application of mistaken rules, it (19.) In the present rage for innovation, and for must yet advance with success, if the principles of the Inductive Logic be rigorously applied to it. In

In which beset the Philosophy of the Mind. Many of the reasonings
all the other Sciences, the progress of discovery has of Stewart, such is their truth and generality, are as applicable to

Physics as to Metaphysics.
* Stewart's Philosophy of the Mind, vol. i. p. 400, 3d edition. Essais sur l'Hygrométrie, ch. x.
| De Gerando, Hist. de Systémes, tom. ii. p. 481, 482.

+ This beautiful and highly Philosophic maxim is taken from
We have here applied to Meteorology what the eloquent Dugald Stewart's Outlines of Moral Philosophy, p. 4, 4th edition, and is
Stewart has with so much truth said respecting the peculiar difficulties peculiarly applicable to the subject before us.

tion."*

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