ology.

tory observations.

Meteor (1.) THE Condition of Man is so intimately connected with the various phenomena of the atmosphere, that he may, without impropriety, be regarded as a MeteoroloIntroduc- gist by nature. In all the varied circumstances of his state, whether as a wild and uncultivated savage, exposed to the fury and inclemency of the weather, or in the first stages of his civilization, when he has discovered some feeble means by which he can shelter himself from the descending torrent and the scorching energy of the sun; or when, as a shepherd and agriculturist, his interest leads him to watch with more anxiety the varying connection aspect of the sky, or as a mariner to connect the agitaof Meteor- tions of the ocean with the terrible force of the sweepology with- ing wind, he finds much of his happiness, and, at times, the condi- even his safety and existence, identified with the mighty tion of Man. and changeful character of the great fluid ocean, in which it has pleased the Almighty to place him.

Intimate

Dicult to

trace the

tory.

Causes

(2.) It would be difficult to trace the probable steps by which Man, during a long succession of Ages, has arrived steps of its at his present limited knowledge of atmospherical phenoearly His mena. The great causes which impeded the general march of Physical Science, necessarily exercised their influence on this branch as on others; and when we consider the peculiarly intricate conditions connected with every atmospherical problem; the large advances that must be made in many capital portions of knowledge, before one successful step can be made in this; the subtile which have nature of the medium which is the subject of investiretarded its gation; its singular relations to moisture; the changes it undergoes with every alteration of temperature; in one region influenced by the full power of a vertical sun, and in another chilled by the frozen masses of the Polar zones; altering its circumstances on lofty hills, and again assuming new conditions in valleys; the islands of the West receiving the air that a few hours before lingered over the countries of the East; the warm breath of the South softening the rigours of the colder regions of the North; the vapour rising from the bosom of the Atlantic, dropping richness and fertility

advance.

ment.

VOL. V.

(3.) Meteorology, therefore, is not an insulated de- Connected partment of knowledge, detached from every other, but with many is intimately related to many of its most important of the most interesting branches. With Chemistry, for example, it stands con- teref nected in a highly interesting manner, and is blended knowledge. with almost every page of its splendid History. The Chemical constitution of the atmosphere, must at all With Chetimes have been an interesting object of research; and mistry. in later days, when this beautiful branch of inquiry has assumed so perfect a form, and unravelled so many of the hidden mysteries of Nature, its relations to Meteorology have been contemplated with redoubled interest. With the properties of Heat, and with the Heat. distribution of temperature over the varied and unequal surface of the globe, Meteorology necessarily holds an intimate connection. The principles are singularly curious which mark the gradations of climate, and disclose the Gradations interesting system of changes by which the atmospheric of climate. currents are produced; and a fertile and instructive branch of inquiry is opened by tracing, amidst the apparent uncertainty which characterises these diversified operations, something like the existence of laws; and by endeavouring to embody, in general analytical forms, representative values for them. It is thus that the Meteorologist has been enabled to obtain at the level of the sea, an approximative value of the temperature of his place of observation; and it is some evidence that a few successful steps, at least, have been made in the inquiry, when the mean temperature of a place can thus be obtained, sometimes within the fraction of a Gradations degree. Connected also with the same inquiry, is the of temperconsideration of the laws which mark the gradations ascend of temperature, as we ascend above the Earth. There above the are approximative laws which the ingenuity of the Earth.

B

ature as we

Meteor

ology.

Plane of perpetual frost.

Scientific Meteorologist has reached, which connect the temperature of the loftier regions of the air with that of strata more accessible to Man; and in following up the gradual system of changes which mark the decrements of Heat, to the point at which water congeals, he has been enabled to fix in every latitude the limits of perpetual frost in the air; tracing it to its greatest point of elevation between the tropics, following it as it descends in the temperate regions, until it Vicissitudes sinks to its lowest possible level in the frigid zones. In of this great tracing also the varying altitudes of this magnificent plane. plane during the uncertain vicissitudes of the seasons; marking its ascent during the tide of summer, and its descent when chilled by the blasts of winter; its Northern portion rising, when by the increments of the solar declination the temperature of Europe and Asia are augmented; or its Southern portion falling, as corresponding regions of the globe lose a part of the sun's vivifying power, the subject has become connected with many other departments of the Natural Sciences, with the Geographical distribution of plants, for example, and has given to Meteorology another claim to high and attentive consideration.

Radiant Heat.

tion.

(4.) With all the inquiries connected with radiant Heat, the subject of Meteorology is also most intimately connected. The atmosphere is influenced in different forms by the innumerable objects of the material world, each having a radiating power of its own, and all exercising an influence on the air. To trace in their fullest Solar radia- extent all the conditions connected with solar radiation, it became necessary for the Meteorologist to measure its effects in different latitudes; to follow its changing influence through the different months of the year; to estimate its progress during the several hours of the day; to trace its power on the varied tribes of vegetation; and to discover, under all its diversified Terrestrial circumstances, its maximum force. In like manner, in radiation. order to trace the laws which regulate terrestrial radiation, the Meteorologist has found the extent of its power in different latitudes; compared its influence upon plains and mountains, and measured its effects in the several months. All these inquiries have much extended the labours of the Meteorologist, and opened to him most fertile and instructive fields.

Density of the air.

Incessant

(5.) While, by the agency of the Thermometer, these interesting phenomena have been disclosed, the Barometer has unfolded the most singular relations respecting the density of the air. The early cultivators of Meteorology must have almost despaired of being able to trace fluctuations, any thing like uniformity, amidst the incessant fluctuations which the Barometer displayed. Influenced, apparently, by a multitude of capricious causes, it must have seemed as if no clue existed by which any resemblance to a law could be detected; yet later observers, employing instruments of a more perfect construction, and extending their observations over a longer period of time, have arrived at many important conclusions of the greatest interest to Meteorology, and to the Physical Sciences in general. One of the most useful of these, is that equality of pressure which the mean altitude of the Barometer, at the level of the sea, has in every latitude disclosed, and which, as a standard in so many interesting Physical investigations, is of Applications of the very great importance. In the applications of this Barometer instrument, also, to many important objects connected to Physical with Physical Geography; in making us better ac. Geography. quainted, for example, with the varied irregularities

Meteor

ology.

which have

existing on the surface of the globe; determining the altitudes of the loftiest mountains, fixing the elevations of the sources of rivers, and of the positions of cities which the enterprise of Man has reared, in many situations far above the level of the sea; and making known, in all its minutest forms, the exact conditions of the terrestrial surface, an interest of the most important kind is given to this application of the resources of Meteorology. The refinements, also, which Refinements have been introduced into Barometrical measurements, been introby the employment of corrections; for the influ- duced into ence of capillary attraction, and the accession of the Barometriminutest atoms of moisture; the varied shapes which cal measurethe ingenuity of the analyst has given to the for- ments. mule of computation, all impart deep interest to this important branch of Meteorology. But it is from Atmosphethe delicate and uniform changes which the atmo- ric tides. spheric tides display, that the Barometer becomes most important. In the torrid zone, these remark- Their reable oscillations are disclosed with such admirable markable uniformity, that the Meteorologist contemplates the uniformity in the torrid horary changes of the mercurial column, with a part of the certainty which marks the anticipations of the Astronomer. And even in the more varying regions of Discoverthe temperate zone, where the changes from heat to cold able also in are most capricious, and where the winds, ever changing, seem to impress the character of perpetual uncertainty on every thing connected with the Barometer, the Meteorologist has been enabled to detect an analogous system of changes.

zone.

the temper

ate zone.

(6.) The state in which aqueous vapour exists in the Various reatmosphere is also another important branch of Meteor- lations of ology, and has been the object of much anxious in- aqueous quiry. It is connected with all the interesting relations pour to Meteorology of the Hygrometer; with the series of laws regulating the force, the weight, and the expansion of vapour; the discovery of the term at which precipitation takes place from an alteration of temperature; the rate of evaporation under different temperatures and with different velocities of the wind; the consideration of the alteration of volume which air undergoes from Heat, and from the accession of vapour; its alterations of density, and the changes of its Specific Gravity in different states of saturation.

(7.) The subject of dew likewise unfolds to the in- Dew. quiring Meteorologist very interesting properties. No other investigation developes in a more perfect manner the singular relations of radiant Heat, and the laws by which caloric is communicated from one body to another. The vegetable world in particular opens a fertile and most interesting train of observation. Of the different grasses, each draws from the atmosphere during the night a supply of dew to recruit its energies, dependent on its form and its peculiar radiating power. Every flower has a force of radiation of its own, subject to changes during the day and the night; and the deposition of moisture on it is regulated by the peculiar law which this radiating power obeys; and this power will itself be influenced by the aspect which the flower presents to the sky, unfolding to the contemplative mind the most beautiful examples of creative wisdom.

(8.) With the phenomena of rain, its primary forma- Rain, hail, tion, and the principles which regulate its descent; the snow, formation of hail, the consideration of the laws that occasionally impart to it its beautiful crystalline forms; the still more delicate creation of snow, and the in

vestigation of the endless groups to which particular

ology.

Meteor conditions of temperature, and the peculiar circumstances attendant on the vapour actually existing in the air give birth, it is needless to say how closely Meteorology is connected.

Clouds,

baloes,

(9.) The formation and classification of clouds, the varied and incessant changes which they present; the carona, &c. laws which regulate their suspension, and their gradual and sometimes sudden destruction by rain, belong all to this branch of Meteorological inquiry. So also the consideration of the laws which appear to influence the formation of haloes, coronæ, parhelia, &c. all of which owe their origin to the presence of aqueous particles existing in the air, place Meteorology in a most interesting relation to Light.

Electrical

(10.) With all the phenomena of Electricity, the phenomena. Meteorologist has claimed an intimate connection, ever since Franklin identified lightning with the ordinary electric fluid. The first conception of the thunder rod, was one replete with magnificence. To draw down silently from a cloud the matter, which, if discharged, would hurl destruction upon thousands, and destroy the finest monuments of Art, is an operation which seems to impart to the feeble hand of Man, a portion of the power of the Supreme. The beautiful phenomena of the Aurora Borealis. Borealis, illuminating by their splendour those unexplored regions of Nature, which are covered at all times with a hoary desolation; their occasional descent into the temperate zones of the Earth; and the influence which their changeful coruscations is said to exercise in particular cases on the Magnetic needle, have identified in an especial manner the Science of Electricity with that of Meteorology.

Aurora

W.nds.

(11.) The general theory of winds, and their many modifications, opens also another interesting and instructive field of Meteorological inquiry. To trace the sources which produce those tremendous hurricanes and storms, that spread desolation over the fairest prospects of Nature, and which communicate likewise to the ocean its awful character and power; to consider the causes also of local winds; to account for the economy of Nature, in providing for the inhabitants of the tropical regions the refreshing interSea and changes of sea and land breezes; and for the existhand breezes ence of those periodical winds, which in some of the regions of the Earth perform, for definite periods, with the most exact uniformity, their stated and particular courses; facilitating the objects of navigation, and impressing a character of uniformity on the latitudes in which they abound; these, and many other inquiries of an analogous kind, awaken in an uncommon degree the attention of the Meteorologist.

Natural

History Indications of animals.

(12.) The cultivation of Meteorology is connected also, in an especial manner, with many of the departments of Natural History. With the habits of particular animals it is intimately identified, the sagacious observer being enabled to anticipate many atmospheric changes from an attentive observation of them. The common Swallow has always been considered as a weather-guide; and not only may the approach of rain be expected when she dips her wings in the stream, but even the gradations of climate may be marked by her approach. The voice of the solitary Crow, the clamours of the Pintado, and the activity of Ants, are all indications of coming rain; and by the mariner, the approach of the stormy Peterel, seeking for shelter under the wake of his vessel, is regarded as the harbinger of a storm. So that of the Fulmar to land,

is a sign to the inhabitants of St. Kilda, that the West Meteorology. wind is very distant from them.

(13.) With the most exalted branch of Physical Meteorology knowledge, Astronomy, the Science of Meteorology useful in stands in many interesting relations. In determining Practical the exact situation of a celestial object, the conditions Astronomy. of the internal and external temperatures require constant observation; nor must the movements of the Barometer be neglected, when the delicate problem of the Astronomical refractions is to be applied. Meteorology has indeed furnished to the latter many of its most important elements.

(14.) In the inquiries also connected with the figure Figure and and extent of the atmosphere, the most beautiful appli- extent of the cations of the law of gravitation have been made. The atmosphere. Mathematician, in considering the figures of the atmospheres of the Planets, is necessarily led, in a peculiar degree, to notice the volume of air surrounding the sphere which he inhabits. Its spheroidal form has called into action the most profound theories of analysis; and the Meteorologist rejoices to find, that the great laws which Newton delivered respecting the system of the World, meet with some of their most interesting applications in that atmosphere, whose incessant mutations it is his constant object to watch and record.

(15.) In this rapid sketch of the relations of Meteor- These difology to some of the leading departments of Physical ferent relaScience, an attractive picture is exhibited of the im- tions of Meportance and value of the inquiry. The Meteorologist, teorology display the while he is engaged, either for his amusement or in- importance struction, in tracing some of the steps of the great and value system of atmospheric changes; in recording the in- of the incessant fluctuations of the Barometer, marking the quiry. vicissitudes of temperature, or estimating the force and influence of aqueous vapour, is thus preparing, sometimes unconsciously, materials for perfecting many of the other Sciences. While his primary object is, perhaps, to arrive at some of the elements connected with the great problem of climate, he is aiding the Astronomer in forming his catalogues of the stars. The inquiry therefore is not only valuable in itself, but is rendered doubly so by the relations which it bears to so many of the other Sciences.

(16.) The condition of Meteorology at the present Present moment is one of very great interest. Much has been condition of attained, and much, very much, remains to be done. Meteorology The chief wants appear to be improvement in the instruments of observation, and unity amongst the observers. To copy the example of the most perfect of the Physical Sciences, Astronomy, it may be remarked, that that splendid department of knowledge has advanced to its present perfection, by the improvements that have been gradually imparted to its instruments of observation, and to the cautious and accurate deductions that have been drawn from their successful employment. In like manner must Meteorology advance, if similar methods be adopted. It is true that the elements connected with the inquiries of this Science are much more uncertain and variable; but an extension of the field of observation, both as regards space and time, must surmount many of them. The successive improvements of the Telescope have revealed to the Astronomer unnumbered clusters of stars; and the Micrometer, advanc ing from year to year in improvement, has enabled him to measure, with unhoped-for accuracy, the minutest intervals of space. So must an improved construction of the Barometer and other instruments employed in

Meteor Meteorological observations, guided by a more cauology. tious spirit of induction, lead, in process of time, to like satisfactory results. When we reflect on the general condition of Physical Science, at the time when Bacon laid down the rules according to which Philosophical inquiries ought to be prosecuted, and contrast it with its condition now; how by the steady application of his inductive precepts many of its branches, which were characterised by uncertainty and doubt, have been reduced to comparative certainty and order; it is not too much to expect, that Meteorology, although still surrounded with so much difficulty and error, will hereafter attain its proper rank in the scale of the Sciences. The indefatigable recorder of atmospheric changes will then no longer be classed with the mere empiric. A survey of the past History of Physical knowledge will lead us to consider this conviction as neither romantic nor unnatural.

Sources of error which

General

theories

seductive.

(17.) The great error which the cultivator of Meteorthe Meteorology has to avoid, is that tendency, which has more ologist has or less existed in different stages of its History, to a to avoid. premature generalization departing from the narrow and cautious path which Bacon laid down. To His objects. accomplish an analysis of all the complicated phenomena of the atmosphere into simple and original principles, ought to be the aim and object of the Philosopher, and it is one well worthy of his lofty ambition and hope. But to proceed with success, "it is necessary to ascertain facts before we begin to reason, and to avoid generalizing in any instance, till we have completely secured the ground which we have gained. Such a caution, which is necessary in all the Sciences, is, in a more peculiar manner, necessary here, where the very facts from which all our inferences must be drawn, are to be ascertained only by the most patient attention."* There is something specious and seductive in all attempts at generalization; and it seems as if the specious and mind, from the influence of improper habits, rather clung to the consideration of general principles, than to those severe and rigorous modes of observation, which the pure principles of the Inductive Logic require. But the History of knowledge is filled with the most melancholy proofs of the absolute futility of all attempts of the kind; and notwithstanding the splendour and success that have resulted from the application of the legitimate rules of Philosophy as laid down by Bacon, we yet find a strong tendency to violate them. It seems as if the mind delighted in hanging every thing on a single point, and adopting some principle as an infallible rule, to make the whole framework of Nature bend to its dictates. "It required nothing less," says an eminent Philosopher, than the united splendour of the discoveries brought to light by the new Chemical School, to tear the minds of men from the pursuit of a simple and primary element; a pursuit renewed in every Age with an indefatigable perseverance, and always renewed in vain;" and the History of Meteorology is filled with like impotent attempts. But checked as its growth has been by the application of mistaken rules, it must yet advance with success, if the principles of the Inductive Logic be rigorously applied to it. In all the other Sciences, the progress of discovery has

46

Stewart's Philosophy of the Mind, vol. i. p. 400, 3d edition. De Gerando, Hist. de Systémes, tom. ii. p. 481, 482. We have here applied to Meteorology what the eloquent Dugald Stewart has with so much truth said respecting the peculiar difficulties

ology.

been gradual, from the less general to the more gene- Meteorral laws of Nature; and it would be singular, indeed, if, in so complicated an inquiry as Meteorology, one which labours under so many disadvantages peculiar to itself, a step should, all at once, be made to a single principle comprehending all the particular phenomena which we know. The Meteorologist must be content, like the cultivators of all the other departments of Natural Science, to advance by careful induction; to interrogate Nature under all her forms, and not to abandon the subject in despair, if her responses be not immediate.

(18.) There is one peculiarity, however, belonging Helps to the Science of Meteorology, which distinguishes it in which a particular degree from all the other Sciences; and Meteorology that is the helps it may receive from popular observa- may derive from poputions of phenomena. Saussure has remarked,* that lar observa"it is humiliating to those who have been much occupied tions of in cultivating the Science of Meteorology, to see an phenomena, agriculturist or a waterman, who has neither instruments nor theory, foretell the future changes of the weather many days before they happen, with a precision, which the Philosopher, aided by all the resources of Science, would be unable to attain." But there are no just grounds for the humiliation which the Swiss Philosopher has here alluded to; for "the knowledge of the Philosopher differs from that sagacity which directs uneducated men in the business of life, not in kind, but in degree, and in the manner in which it is acquired." And when we consider, that the agriculturist and the waterman are always employed in the open air, with their minds constantly occupied with an object which interests them more immediately than it does the Philosopher, it can be no matter of surprise that they often group together facts, which, like the instinct of animals, serve to guide them in their predictions. The local sign which directs them may Examples.. be a fog which rises at a particular hour, in some peculiar locality, the appearance of a cloud on the summit of a mountain, to which their attention has been directed by many early associations, or the song or migration of certain birds. But if these limited interpreters of Nature be transported to new seats, the symbols which guided them in their own locality will no longer be efficient; and other trains of observation must be begun, to fit them for their new condition. The views of the Philosopher are much more extended and general. His aim is not to limit his conclusions to a More gene single locality, but to develop them under their most ral views of general form; and it is then that the superiority of well- sopher. directed observations becomes manifest. If, indeed, the Scientific Meteorologist could be constantly occupied like the agriculturist and the waterman, in watching the appearances of the heavens, our knowledge of atmospheric phenomena would soon be prodigiously increased; but unable thus to employ himself, it will be the object of the genuine cultivator of Meteorology to draw from the experience of even uneducated men all the helps he is able.

(19.) In the present rage for innovation, and for

the Philo