9["Reid's Law of Storms", The Sydney Morning Herald, Thursday 02 May 1850, page 3]
REID'S LAW OF STORMS.
(From the Times.)
The Progress of the Development of the Law of Storms; and of the Variable Winds,
with the Practical Application of the subject to Navigation.
Illustrated by charts and woodcuts.
By Lieutenant-Colonel William Reid, C.B., F.R.S., of the Corps of Royal Engineers.
This volume forms the sequel to a work which attracted repeated notice in our columns at its first appearance, eleven years ago. Its contents, as is obvious from the title itself, are calculated for the practical use of only a limited class of readers, but so universal is really the interest of the subject, and so striking are the conclusions announced, that we shall be rendering, we are sure, an agreeable service to the public at large by popularizing the information thus communicated, and by stating in a brief and intelligible form the foundation and proofs of this remarkable theory.
In the year 1831, Colonel Reid was officially employed at Barbadoes in reconstructing the Government buildings which had been recently destroyed there by a hurricane so violent that 1477 lives were lost in the space of seven hours. During this engagement the subject of storms and their character was naturally forced upon his notice, and he was induced to search for records of previous tempests, and for any such information, whether traditional or documentary, as might exploin the originating causes of these terrible visitations, or tend to define the manner in which they operated. Nor was he left without some suggestions of the truth. The famous Benjamin Franklin had recorded an observation "that a north-east storm came from the south-west," and the weatherwise people of New York had embodied the same remark in their catalogue of vernacular prognostics. Even seamen had a common proverb that "a north-wester would never remain long in debt to a south-easter," and the inhabitants of some of the West Indian islands actually applied the familiar phrase of "roundabouts" to the gales of the locality. Hints like these were abundantly sufficient to set so able an officer as Colonel Reid on the right track of inquiry, but he presently discovered still more explicit guidance in the published investigations of Mr. W. C Redfield, of New York. He borrowed, however, little beyond the suggestions thus furnished, and resolutely commenced applying himself to the detection of the truth by the legitimate process of experimental induction. For this purpose he collected, from various quarters, all the details of particular storms which chanced to have been authentically recorded. It was soon found that the results were unsatisfactory when the observations in question had been made on shore, and indeed it almost appeared that the proverbial notions concerning the uncertainty of the wind were not likely in this particular to receive any correction from the discoveries of science.
Allowance, however, was made for the effects probably producible on a gale by the irregularities of the earth's surface with which it came in contact, and the inquiry was more steadily pursued by means of observations made at sea. The logs of all the vessels known to have encountered any particular storm were carefully collected and compared, and their successive positions hour by hour during the period of tempests were marked down upon a chart, together with an exact notification of the quarter on which they were receiving the wind at such moments. Ihe collective results of these communications furnished the means of tracking not only the course of the storm from one latitude to another, but the directions successively taken by the atmospheric current itself. When the investigation had been once instituted, there was little lack of materials. For some storms the logs of as many as thirty vessels were found to be forthcoming, by which the action of the wind from one hour to another became almost continuously determinable.
From the evidence thus obtained, it soon appeared highly probable that the action of nature in these atmospheric convulsions was regular, and that tempests moved and operated according to a fixed law. The development of this law by means of facts, arranged according to place and time, became now the great object of Colonel Reid's endeavour, and it is the success or "progress" of this development up to the present moment which he has communicated to the world in the volume at present under review. The following are the chief conclusions of the theory which have now been strengthened by the experience of eleven years:
1. Great storms aro progressive whirlwinds; that is to say, they are portions of the atmosphere in a state of rapid revolution, and having, besides this motion round their own vortices or centres, a general progressive motion at a variable rate of speed.
2. In tropical latitudes, the first of these motions takes opposite directions on opposite sides of the equator--that is to say, the whirlwind revolves one way in the northern hemisphere, and the opposite way in the southern, from which conclusion it directly follows that such a storm could not pass the equator without subsiding, as its mode of revolution would be reversed.
3. The progressive motion of these whirlwinds within the tropics is generally from east to west, until they reach the 25th or 30th degree of latitude, and incline towards the poles, when they recurve again to the eastward, in opposite directions, according to the hemisphere in which they are situated. Their rate of speed is found to vary from three to forty-three miles per hour; and it is even thought that at some particular period, such, for instance, as the moment of rccurvature, their progress is below the lowest of these rates. Presuming the whirlwind to be stationary, its figure would be correctly represented by a circle, and such figure indeed approximates so nearly to accuracy, that it is usually employed on the storm charts; but in case of a progressive whirlwind, the figure would of course become cycloidal, or, in other words, it would resemble a common coil of rope somewhat opened out. It is rather difficult to put diagrams into words, as the reader may perhaps discover, but we must do our best to define the fundamental propositions of the theory, and the practical results will soon be found in the highest degree interesting.
According, therefore, to this theory, a storm is a convulsion of a limited portion of the atmosphere, assuming a known configuration, and moving in an ascertainable direction, whence it follows that such storms may be sailed out of, or overtaken and sailed into, and even, under certain circumstances, scientifically avoided, of all which incidents examples have been supplied by actual practice. The subject of inquiry thus becomes twofold; first, as regards the revolution of the whirlwind itself, and next as regards its general progress or track. The discoveries on the former of these points have gone far to elucidate one of the great mysteries of nature in the action of the barometer, and to explain the true cause of the rise and fall of the mercury during a storm. When an extended portion of the atmosphere has bren set in a state of revolution, a centrifugal action is necessarily created by such movement, and, by consequence, the atmospheric pressure at certain parts of the earth's surface is proportionately diminished. A familiar exemplification of the principle alluded to will be given by a tumbler half full of water in a state of rapid revolution. If the tumbler, while the water is thus revolving, be held up to the light, the surface of the liquid representing tbe atmosphere, will be seen to be depressed in the centre of the whirl. An atmospheric whirlwind acts in a similar manner, by diminishing, as we have said, the pressure upon the earth's surface, and most of all in the centre of the whirl or storm, so that as the mercury in the barometer feels this diminution of pressure at the approach of a storm it begins to fall, and will be at its lowest when the centre of the storm is passing over the spot, i.e., in the thickest of the tempest, but will again recover itself after this is past, and will gradually rise as the influence of the whirlwind is removed and the atmosphere regains its usual gravity. It will thus be seen, that what the barometer foretells is, emphatically, a storm, for its action is exclusively due to the rotatory motion distinctive of these convulsions, whereas strong straight blowing winds may occasionally occur with a very high barometer. But these are not the tempests whose destructive powers are so often recorded. All such visitations, whether termed typhoons, hurricanes, or tornadoes, are progressive revolving gales, and in these the wind veers and the barometer falls.
It is this veering, or gradual changing of the wind, which is so characteristic of a tropical storm. Most readers will recollect that in the narrative of shipwrecks, and such like catastrophes, which amused their earlier days, it was an almost invariable incident of the story that the wind blew successively from all parts of the compass, and that the waves chopped and crossed each other with inconceivable fury. This was in consequence of the revolving charactor of the gale, and the same consideration will explain the familiar occurrence of a ship's suddenly righting herself in the midst of a storm beyond the hopes, and apart from the efforts of the crew. There are also two other incidents of great storms which receive an instructive elucidation from this theory. One is that deceptive lull of the wind followed, after a short interval, by a renewal of the gale from an opposite quarter, and which is occasioned by the vessel's passing through the centre of the storm, and then entering its opposite half. The other is that singular phenomenon, termed by Spanish sailors El ojo, or the storm's eye, when in the midst of a black and lurid mass of clouds there appears a luminous circle in the zenith. This is the very centre of the whirlwind, and a remarkable illustration of all the conditions of the case is given in the log of the Marmion, bound from Liverpool to New York, under an intelligent captain, in the December of last year. It had been blowing with great violence and with a tremendous sea all the morning, till it suddenly began to slacken, and "at noon it was quite moderate, and a beautiful clear, blue sky, and the sun shining beautifully, but this is in the treacherous centre. From meridian to about 0-40 it remained quite moderate and clear. At 0-40 there rose up a thick impervious cloud or haze, and it became quite dark, comparatively speaking, though there was no black cloud; and in a very few minutes we were involved in a terrific storm" The readings of the ship's barometer, taken as she passed through the storm's centre, will exemplify very strikingly what we said upon this subject in a preceding paragraph. Between 6 a.m. and 4 p.m. these were--28.20, 28.11, 28.03, 27.99, 27.75, 27.70 (this was the storm's centre), 27.70, 27.70, 27.75, 27.95, 28.70.
The most complete and convincing illustration, however, of the law of storms, both as regards their revolving character and their progressive motion, is derived from the log of the Charles Heddle. This vessel was a very fast brig, originally built for a slaver, and very ably commanded. She sailed from the Mauritius on the 21st of February, 1845, and soon fell in with a storm, in the southern hemisphere, before which she scudded for five days. She got within the compass of tho whirlwind with the wind at S.S.E., from which "it became S., and continued to the brig constantly veering as she sailed round and round. Thus in the logbook it is next recorded that she scudded N., then N.N E., next N.E., her course changing to E.N.E., to E, to E.S.E., to S.E., to S.S.E., and then to S., when the wind in the log is marked at N. The logbook then shows that her course was changed from S. to S.W., to W.S.W., to W., to W.N.W., to N.W., and to N.N.W., thus completing her first entire revolution round the vortex of the storm." By this time her sails had blown away, and she was reduced to bare poles, but she still continued changing her course in the same manner, and scudding, until she had made "five complete circuits, wanting only four points of the compass, round the vortex of the storm, by steering always before the wind."
When we come to investigate more closely the second of the two motions of a storm, namely, its progressive motion or track across the deep, the interest of the subject increases still further. In some quarters of the globe great numbers of gales and storms have now been tracked for more than 2000 miles, and every particular relating to their progress and direction has been accurately noted. Generally, as we have stated, in tropical latitudes, storms are found to move from east to west up to a certain point, and then to recurve. Their tracks or orbits, too, are found to be tolerably constant, although the investigations on this head have not been hitherto pushed with equal zeal in all ports of the world. The best known sea, fortunately, for our Liverpool traffic, is the North Atlantic, and the frontispiece to the volume before us is a hurricane-chart showing the tracks of some l8 or 20 well known storms over these waters. These whirlwinds appear to take their origin somewhere in the lowest degrees of north latitude and about west longitude 40, from which point they move westward, inclining to the north, over the Caribbean Sea, pouring their full force upon our luckless West Indian plantations. Still moving west, they sweep the south eastern coast of the United States, occasionally, though not often, penetrating inland, and making their return curves to the east, somewhere about Cape Hatteras, as was the case with the West Jersey tornado, described in our paper a few weeks since, and which, at Capo May, was found blowing furiously eastward. From Cape Hatteras they blow directly in the teeth of our Halifax bound vessels, or sometimes take a northerly sweep over Newfoundland or Labrador. The Bay of Bengal storms, too, have been most laboriously tracked and illustrated, as have also, to some extent, the typhoons oí the China Seas. In prosecuting this latter branch of inquiry, Mr. Piddington, a most able and successful labourer in this field of science, betook himself to the records of the East India Company in order to investigate the logs of Indiamen in days past, and thus test a modern theory by the undesigned testimonies of a preceding generation. One of his extracts ought to carry unusual interest in the reader's eye. It comprises the logs, during a storm in the Chinese Seas in 1803, of the Hon. Company's ships, Warley, Royal George, Bombay, Castle, Alfred, Coutts, Ganges, and Earl Camden,--being the identical vessels which, four months later, under the broad pennant of Commodore Dance, in the Earl Camden, engaged and repulsed Admiral Linois with the Marengo, Belle Poule, Sémillante, Berceau, and Aventurier. The stormtracks of the East Atlantic have been but very imperfectly ascertained, though there is reason to suppose that the Madeira gales do not differ except in degree of force from those of Bermuda. The characteristics of the Arabian Sea, too, in this respect have yet to be established, but, as spe- cial attention to this subject is now enforced on board the mail steamers of the Peninsula and Oriental Company, our information may be speedily expected to improve. The neighbourhood of the Andaman Inlands seems to be a favourite spot for the generation of these whirlstorms, whence they traverse the Bay of Bengal and burst upon the south-east coast of India, but, being checked by the high line of eastern ghauts, they find an issue by Salem across the Coimbatore plains, and escape through the Palogatchery Pass into the Arabian Sea in the exact direction of the Laccadives.
The practical application of all these discoveries to the science of navigation, though, one of the principal objects of the publication now under notice, is obviously a branch of the subject on which we can touch but lightly. The value, however, of the knowledge thus communicated can scarcely by set at too high a price. By acquainting himself with the law which regulates the revolution of a windstorm, the commander of a vessel may sail away from its centre. By observing how the wind begins to veer, he can ascertain exactly into what point of a circular storm he is falling, and can take his measures accordingly. Rules are even supplied for the proper nautical evolutions, under certain circumstances, and Mr. Piddington, to whose successful researches we have before alluded, has published a volume, entitled "The Sailors' Hornbook of the Law of Storms, in all parts of the World" A general knowledge of the progressive motion of storms will secure even still further immunities, as the tempest can occasionally be escaped by judicious movements, like a shower of rain in a morning's walk. For this purpose, it is necessary, of course, to obtain prognostics, which are supplied in the first place by the barometer, and, in the next place, by careful observations of the swell. More than one unhappy voyager, after leaving Dover without a breath of air apparently stirring, has found himself tossed off his legs before reaching Calais, and has had to glean his comfort from the explanation of the captain, that "the sea often makes before the wind." It does so, however, in sober reality, the undulations being propelled in certain directions from the circumference of the coming windstorm, according to presumed rules, which we could hardly express without employing some very hard words. But the quarter from which the tempest is approaching can be at least reasonably conjectured from this swell, which is an almost invariable harbinger of the storm itself.
I was in Bermuda, (says Colonel Reid,) when the hurricane of 1839 occurred, and distinctly heard the sea breaking loudly against the shores on the morning of the 9th of September, full three days before the storm reached the islands. At that time the hurricane was still within the tropic, and distant ten degrees of latitude. As the storm approached, the swell increased, breaking against the southern shores with louder roar and great grandeur, until the morning of the 12th, when the whirlwind storm reached the Bermudas and set in there. When it had passed over, the northern shore became calm, and the northern reefs in their turn presented a white line of surge.
Sometimes a ship can venture on crossing the front of a storm, at other times it can avoid overtaking it by slackening soil or changing its course, and at all times it can ascertain its position relatively to the storm's centre. The earliest and surest warnings are given by the barometer. An admirable story is told of the use to which these prognostics and their deductions were once turned in the China Seas by Captain Hall in the ship Black Nymph. He was three or four days' sail from Macao, when he noticed, that though the weather was remarkably fine, his barometer was continually falling. Incredulous at first, he at length, when the downward tendency of the mercurial column was put beyond question, made his ship all snug for a storm, to the great surprise of his crew, who were smartening things up for harbour. His next step was to watch very carefully for the first breath of the typhoon, which in due course made itself felt, and he then betook himself to calculate his position, according to such scientific deductions as we have been describing. Tho result was a conclusion that the ship must be on the western and southern verge of the storm, and her course was shaped accordingly, with the following consequences:--
The wind rapidly increased in violence, but I was pleased to see it veering to tho N.W., as it convinced me I had put tho ship on the right tack, viz the starboard, standing, of course, to S.W. For five hours it blew with great violence but the ship being well prepared rode comparatively easy. The barometer was now very low, the wind about WNW, the centre of the storm passing doubtless to our right.
Thinking it a pity, as the gale sensibly decreased, to be so far out of our course, I wore to N.W., and made sail, but in less than two hours heavy gusts came on and the barometer began to fall. I now thought we were approaching the storm once again, and doubtless the theory is not mere speculation. I wore again to the S.E., and to show more clearly how great a difference a very short distance nearer to or farther from these storms makes, the weather rapidly improved.
When we arrived at Hongkong two or three days afterwards, we found they had had a gale, and its centre lay between the ship and Hongkong, through which centre I might have had the pleasure of passing if, regardless of the indications of the barometer, and the results of the scientific comparison of the data of other storms, I had been eager merely to keep on the tack nearest my course.
Other striking instances of successful calculation are given by Colonel Reid. In 1839, Mr. Redfield wrote to him from New York, stating his conclusion that the September gale of that year, to which we have alluded above, must have passed over Bermuda, and so correct was the estimate, that the centre of the storm touched the westernmost part of the island. On the occasion of the same storm a vessel full of passengers hod left Bermuda for New York two days before the gale set in. Of course the most painful apprehensions were entenained by the relatives of those on board, but Colonel Reid betook himself to his charts, laid down the course and distance of the vessel, calculated the track of the storm, and pronounced that, though within its circuit, she would be beyond danger--results which proved literally true. Six years later, that is, in October, 1845, Mr. Redfield wrote again from New York, expressing his fears that the Halifax packet would encounter one of two specified gales which had taken a more easterly course than usual. She did so, and just after her arrival came the other gale, on the east side of the Bermudas Some people may perhaps think such calculations as remarkable as those of an astronomer.
We have been treating almost wholly of tropical latitudes, for it is in these that suth storms most usually arise. But the winds which occur in extratropical latitudes, termed the "Variables," are considered by Colonal Reid to admit of reduction to certain laws, by pushing to their legitimate conclusions the discoveries established in equatorial regions. On this point, however, we have not space to enter, but we have already, we trust, made it evident how far the domination of science may be extended over these hitherto intractable operations of nature. One thing which will not fail to strike most forcibly the attentive reader is the extraordinary combination of seamanship, intrepidity, sangfroid, and resolution, which is disclosed by the various logs of the merchantmen collated and published m these researches. They were intended to convey nothing but the details of the storm, but they unintentionally discover traits of national character and individual ability which are enough to induce very serious doubts whether the merchant service may not recently have been somewhat too lightly spoken of. We must conclude with observing, that it is indispensable to the progress of this wonderful and important science that merchant seamen should unhesitatingly publish to the world the results of their experience, on which point we allow one of themselves, Captain Freeman, of the Sea, to address the others, for we are sure we could find no better language:--
In point of ascertaining the extent of hurricanes in the Atlantic--that must rest with seamen and it might soon be decided if they would only give the subject the attention it deserves and communicate their observations. Many perhaps feel a backwardness in writing anything that will appear before the public, for various reasons, and one no doubt often is, that they feel conscious that they have no great ability. To be plain, they do not in many instances feel competent to pen their thoughts in a way satisfactory even to themselves. Neither can I. But if any man chooses to ridicule my want ot learning or ability let him do so. My only answer is, had he been situated as I have (at sea since I was 12 years of age), perhaps he would not have been a greater profident in learning than myself. Therefore I shall not refrain because I am not talented, and I hope I shall be careful not to be presumptuous or dogmatical when showing my opinion.