« ZurückWeiter »
breadth of the storm, therefore, may be estimated as between two hundred and fifty and four hundred miles, - the
duration depending upon its extent and the velocity with which it moves.
On that portion of the track nearest to the American coast, or the farthest inland, if the storm overlies the continent, the wind begins to blow from the eastern or northeastern point of the horizon, and veers by the north to the northwest, where it terminates. These are known as the northeast storms of the Atlantic States, which are most severe in the beginning, are attended with rain or snow, and generally end with a wind at the northwest, bringing fair weather.
Such are the leading general facts, ascertained by Mr. Redfield, concerning the operations of nature in great storms, particularly those of the United States, and the hurricanes of the West Indies. They are carefully deduced from observations and experiences endlessly multiplied ; and the leading proposition of the rotary motion is fortified by so wide an induction, that we have no hesitation in speaking of it as a truth satisfactorily demonstrated. Mr. Redfield's views are corroborated by Professor Dove, of Berlin, who, without any knowledge of Mr. Redfield's labors, arrived at similar conclusions at about the same time. It is not to be supposed, however, that the rotary storm, though probably the greatest, is the only disturbing cause of the regular atmospheric currents. * Mr. Redfield, whose aim has been, “ first, to resolve particular facts into other facts more simple and comprehensive ; and, secondly, to apply these general facts (or, as they are usually called, laws of nature) to the synthetical explanation of the phenomena " t of storms, was not anxious to indulge, in his earlier papers, in speculations concerning the origin of the phenomena, whose active force he was investigating. Science has not yet determined the part, (probably an important one,) which electricity takes in their production.
But it is less difficult to assign a cause for the mechanical
* We should be glad to present our readers with the outlines of Professor Dove's “ General Theory of the Winds,” and of the admirable essay of Mr. Brown (Phil. Mag.,) in which the views of Daniell are so extended as to embrace hypotheses of the general currents of the atmosphere. But we must keep within the narrowest limits of our subject, -clouds, and storms."
disturbance of the atmosphere, which will result in the formation of aërial whirlpools. Maupertuis, while engaged in his geodesic operations at Tornea, observed that, on opening the door, the external air immediately produced a whirlwind in the room, which was discernible by means of the con
On an occasion in St. Petersburg, when a crowded assembly were suffering from the closeness of the room, a gentleman broke a window for relief, and the air rushing in, formed a visible condensation of snowy matter, having a revolving motion.* It appears, from these anecdotes, that, if a body of air in a quiescent state, at an elevated temperature, and highly saturated with vapor, be suddenly penetrated by a cold current, an aërial vortex will be instantly formed.
Mr. Redfield has met with an able and efficient coadjutor in Lieutenant-Colonel Reid, of the Royal Engineers, who, having been employed at Barbadoes in reëstablishing the public buildings blown down in the hurricane of 1831, had already conceived an interest in the study of the nature of storms, when he read a paper by Mr. Redfield in “ Silliman's Journal,” for April
, 1831. In his valuable work, he has not only laid down in a beautiful manner and with scrupulous fidelity the data furnished by Mr. Redfield, but he has also collected numerous accounts of other storms in both hemispheres. To his industry in compiling and arranging curious and important facts must be awarded high praise ; but to his modesty and candor no praise, however high, can do more than justice. Upon all topics which he discusses, he has been studious to collect authentic information, and whenever he has been carried into the field of conjecture, he has advanced with that sedate caution and steady regard for certain knowledge, undisturbed by the vanity of speculation, which become the philosophical inquirer. Colonel Reid was the first to illustrate the reverse motion of storms in the southern hemisphere. The most interesting of his records upon this point are those of the storm of March, 1809, encountered by the fleet of the East India Company, under the convoy of the Culloden, bearing the flag of Rear Admiral Sir Edward Pellew, the first Lord Exmouth. It has left a deep impression upon many minds in England by the great loss of life and property it occasioned.
Harvey's Treatise on Meteorology, - Encyclopædia Metropolitana.
The fleet had crossed the equator, and sailed on its homeward passage with fine weather, until the 11th of March, when the gale came on. They were then in the vicinity of the islands of Rodriguez and Mauritius, a region which, on the opposite side of the line, corresponds to the West Indies in its stormy character. On the 14th, the fleet was dispersed, and this circumstance afforded the means of obtaining simultaneous observations of the wind in different sections of the storm. After travelling obliquely to the tradewind, from the east to the west, inclining southerly, the storm recurved at the twenty-fifth and thirtieth degrees of latitude, and went off to the south-east, in remarkable conformity with the manner in which the hurricanes of the northern hemisphere pass off to the north-east. The brig of war Harrier was lost, and four of the East India Company's ships, the Lady Jane Dundas, the Jane, Duchess of Gordon, the Calcutta, and the Bengal. The four latter were seen for the last time on the 14th, and probably foundered near the centre of the storm, towards which they were then steering
Colonel Reid has also accompanied Mr. Redfield in his inquiry into the phenomena of water-spouts and whirlwinds. He considers it by no means certain, that the same law of nature produces the small whirlwind and the great storm. We know of no authentic observation, however, except that made by Colonel Reid himself, at Bermuda, which combats the opinion of Mr. Redfield, that the course of rotation is the same in both. The whirling motion of the air satisfactorily accounts for the fall of fish,* and showers of sand, seeds, blood, (a misnomer for red earth, probably,) and salt rain, of which many instances are related both by Colonel Reid and Mr. Espy. Colonel Reid has also applied the diminution of the atmospheric pressure in the centre of storms to explain the extraordinary high tides, and consequent inundations, that often prove more disastrous than the wind. A fall of two inches in the barometer indicates a
* A curious case of the fall of fish in a storm is recorded in The Athenæum for October, 1840. It occurred in the Madras Presidency, sixty or seventy years ago, and a sufficient number was gathered to make a curry for the General's table.
66 Piscium et summa genus hæsit ulmo
Nota quæ sedes fuerat columbis."
3+3 diminution of one fifteenth in the atmospheric pressure, which would cause the sea under it to rise iwo feet. A ware of the sea, answering to the atmospheric wave, may more onward at the rate of the storm's progress, accompanying it in its course, and its height will depend upon the reduction of the atmospheric pressure, modified by the revolving power of the wind. When an impulse, thus acquired, has been maintained for some distance, a current will be created, similar to the tidal wave, and of sufficient strength, when added to the flood tide, to cause the inundations that often occur in flat lands. A storm five hundred miles in diameter, carrying with it the diminished pressure of one fifteenth of the column of mercury, seems adequate either to arrest or accelerate existing currents, or to create new Sir Thomas Hastings saw, during a rapid fall of the barometer, at Portsmouth, an ebbing tide stop, and return to the flood, before its period had elapsed. A well attested fact like this proves the correctness of the Colonel Reid's views.
“ The apparent connexion of storms with electricity and magnetism” is a subject of the deepest scientific interest. The quantity of electricity developed in violent storms is very great, and has, at times, if the accounts can be relied on, affected the needle to such a degree, that it ceased to be of any use.
Colonel Reid ascertained, by experiment, that the two poles of the magnet, in conjunction with the voltaic battery, moved in a manner corresponding to the revolution of hurricanes in the northern and southern hemispheres. Great storms of periodical recurrence are confined, as is well known, to certain parts of the globe ; and it is a curious fact, that the meridians passing through the two portħ magnetic poles run also through the Chinese sea, and near the Caribbean sea, - the regions of typhoons and hurricanes; and that here, the magnetic intensities upon Major Sabine's chart of isodynamic lines are strongly marked, whilst at St. Helena, where a gale is rarely known, the intensity observed by Captain Fitzroy is 0.84, “the lowest denomination recorded."
But we resume the examination of the rotary law of storms, which,
as we before observed, is the general fact, confirmed by Professor Dove and Colonel Reid, deduced by Mr. Redfield from the particular facts he has accumulated. The question is, Do the particular facts sustain Mr.
Redfield's law, and does the law account for the phenomena of storms included in its classification ? The negative answer is stoutly maintained by Mr. Espy of Philadelphia, whose work on the “ Philosophy of Storms” stands at the head of our article. Mr. Espy has been known to the public for many years as a writer in the “ Franklin Journal subjects of science, but chiefly upon meteorology. In 1836,* he published a series of essays, containing a theory of the formation of clouds, and rains, the aërial meteors known by the names of storms, tornadoes, whirlwinds, waterspouts, &c., some of the elementary principles of which are to be found in his earlier papers.f The greater part of the “ Philosophy of Storms " is a republication of his essays and papers in the “ Journal.”
His theory is at once simple and comprehensive, and, as " the probability of a hypothesis increases in proportion to the number of the phenomena for which it accounts, and to the simplicity of the theory by which it explains them,” # if the facts cited by Mr. Espy were to be received without hesitation, we should be as ready to yield our entire assent to its propositions, as we are to admire the ingenuity displayed in its invention. Mr. Espy repeats the doctrine of Brande, that the winds in a great storm rush impetuously from all parts of its outer boundary, either towards a single centre, or, when the storm is of an elongated form, towards a diametrical line which is the longer axis. Whether this opinion be borrowed from Brande or not, it is a necessary conse: quence of the new theory. To support this view, Mr. Èspy also appeals to facts, and to the very facts adduced by Colonel Reid and Mr. Redfield, as evidences of the rotary motion. He has been active in collecting records for himself, but the storms of 1780 and 1837 are presented in his book as most striking illustrations of his theory, and their application is the more conspicuous, as they are selected from Colonel Reid.
It behooves us, then, to examine this question, and, to render the subject more intelligible, we will make the necessary projections. In doing this, it will be our object to test Mr. Espy's merit as an observer and recorder of facts; hereafter, we shall discuss his theory. The following figure represents the progressive whirlwind of Mr. Redfield,
* Franklin Journal, Vols. XVII., XVIII. † Franklin Journal, Nov., 1833, and Jan., 1835. I Stewart's Elements.