THE LAW OF STORMS,

BYEVERETTHAYDEN.(Abstract of a paper read before the National Geographic Society, Nov. 15, 1889.)

In preparing an abstract of this paper it is of course difficult to adhere very closely to the original, inasmuch as that was illustrated by forty-five lantern slides, while it is only practicable to present a few plates with this abstract. I may therefore be permitted to give only a general outline of the subject, with perhaps a more detailed discussion of one or two of the most notable recent hurricanes off our Atlantic coast.

The term "Law of Storms" is applied to the code of rules that should govern the action of the master of a vessel when he has reason to suspect the approach of a dangerous storm. It will be seen that this definition, like the code itself, is somewhat vague. So many considerations enter as factors in the question that it is wholly impossible to lay down any rules that shall be applicable alike to a high-powered, well-manned steamship, and to a heavily-laden, poorly-equipped and short-handed sailing vessel. Disregarding such differences of conditions (which are, of course, of vital importance in each individual case, but which cannot be discussed in a brief general essay), the two grand divisions of the subject may be compared togrand strategyandfield tactics. By this I mean that a broad, comprehensive view of the whole subject of ocean storms—their regions, seasons, size, severity, and tracks—is one very important part of the navigator's duty in planning a long campaign, or voyage; and, secondly, the handling of his vessel when actually in the fight—the coolness, clear-headedness, and trained experience that utilizes every resource of the best seamanship and navigation in a fearful struggle with the fury of a hurricane—all of these are also an essential part of the education of the ideal sea-captain.

Thanks to the progress of meteorologic research it is comparatively easy nowadays for anyone to get a very good general idea of the great hurricane regions of the globe, and the seasons when these dreaded tropic cyclones prevail in each of these regions. The evidence on this subject is cumulative and practically conclusive, so that it is universally known and recognized that the hurricane months are the summer months in each hemisphere; hurricanes originate in the tropics, move westward, then poleward into the temperate zones, and finally eastward in higher latitudes, receding gradually from the equator; moreover, the essential difference between hurricanes north and south of the line is as follows: In the Northern Hemisphere the rotation of the cyclonic whirl isagainstthe hands of a watch, and in the Southern,with. The noted hurricane regions are the West Indies, coast of China and Japan, Bay of Bengal (especially in May and October, at the time of the change of the monsoons), and the South Indian Ocean (about Mauritius). Less noted regions are the South Pacific (East of Australia), the North Pacific (west of the Mexican coast), and the Arabian Sea. In planning a distant voyage a navigator should therefore consider the hurricane regions through which he must pass, just as he considers the prevailing winds—the trades, monsoons, and ocean currents.

The handling of a ship in a hurricane is a very different sort of a thing from this general survey of the entire field, and, without the eminently practical qualities that we all associate with a good officer of the navy or mercantile marine, no mere theoretic knowledge can avail much. And yet this is one of those cases where practice and theory should go hand in hand,—not theory as something vague and unreal, but theory as based upon a firm foundation of observed facts. If a vessel encounter a hurricane, certain conclusions can be drawn from observations of the shifts of wind, the fluctuations of the barometer, the appearance of the clouds, and the direction of the ocean swell; the master of that vessel will undoubtedly draw such conclusions, and store them away in his mind as part of his fund of experience upon which to base action at some future time. But if he can consider his own observations, while fresh in mind, in connection with the observations made on board many other vessels that encountered the same storm, and modify or verify his conclusions by such comparison, there cannot be a doubt but that the lesson will be of far greater value. Sailors lead a rough life, and their training is often acquired by experience alone. Moreover, there are certain things that tend to discourage effort on the part of junior officers, even on board naval vessels: they realize that their duty is not to originate orders but to execute them, and sooner or later they get out of the habit of reflecting upon the action taken to avoid a storm or manoeuver in one, not knowing at the time what considerations lead to the action that was taken, and not always having anything brought forcibly to their attention to indicate with certainty whether the action was well-considered or ill-advised. Upon finally attaining command themselves they are not, therefore, as well posted as they might otherwise have been. I mention these things to explain the undoubted fact that comparatively few masters of vessels are well posted in certain very important additions to the old law of storms, as it was discovered by Redfield and enforced by Reid, Piddington, Thom, and other early writers. In fact, of all the navigators of various nationalities who have charge to-day of the commerce of the world, probably four-fifths are wholly ignorant of the progress that has been made in this direction in the past fifty years. That such is the case is not, in my opinion, wholly their fault: it is owing to the fact that far too little attention has been paid to clear, forcible, and convincing explanation; it is the fault of the teachers, no less than the scholars,—of meteorologists who talk over the heads of their audiences, instead of stating facts and conclusions in a way to command attention and respect from the practical men who furnish the data, and who deserve some tangible results in return for their long years of voluntary observation.

It is difficult to put this matter very clearly to those who are not familiar with the conditions that govern the management of a vessel at sea, and I shall only attempt to do so in a very general way. It should be understood, first of all, that a hurricane is an enormous whirlwind, so large, in fact, that its circular nature was generally recognized only about fifty years ago. At the immediate center of the whirl there is a calm space, from five or ten to thirty or forty miles in diameter, generally with blue sky and bright sunlight. Within a short distance of this central calm the wind blows with frightful violence, and here a vessel is driven along in absolute helplessness, enveloped in midnight darkness, buried in a flying mass of foam and spray, with every sound annihilated by the roar and shrieks of the elements. The core of the hurricane, as this region has been called, is small, relative to the entire area, and it thus happens that a few miles may make all the difference between shipwreck and safety. The question is, then, to avoid getting into the core, or heart, of the hurricane. It is evident enough that if the wind blow in a strictly circular direction around the center, the bearing or direction of the center must be at exactly right angles (eight points) to the right (or left) of the direction of the wind. In other words, in the Northern Hemisphere (where the direction of rotation is against the hands of a watch) the center bears eight points to the right of the wind (that is, to the right of the direction from which the wind blows); in the case of a hurricane off our coast, for instance, if the wind be NE. at Hatteras the center would bear (according to the 8-point rule) SE. Considering, further, that the entire whirl has a progressive motion along a path, or track, if an observer at Hatteras find that the NE. wind freshens rapidly, without any shift or change of direction, it is equally evident that the center of the storm is approaching directly toward that point. In a similar situation at sea, a shipmaster would naturally see that his vessel was in a position of great danger: evidently the best thing to do would be to run before the wind, thus getting out of the way of the approaching hurricane. This simple case will explain pretty clearly, I think, how rules were at once formulated and adopted, as soon as Redfield had proved the approximately circular character of these storms.

Without going further into this subject, inasmuch as this 8-point rule is perhaps the most important of all the rules—indeed, all of them follow directly from it,—suppose that subsequent research, based upon careful observation and the accurate charting of hundreds of reports from vessels in similar storms in various oceans, proved conclusively that the wind in a hurricane does not blow in strictly circular whirls, but rather spirally inward, so that with a NE. wind off Hatteras the center bears probably S SE., or even South: evidently this is a matter of vital importance to the navigator, and all the old rules should be remodeled to suit the discovery. Such is, indeed, actually the fact, and in most cases nothing could be worse than to run directly before the wind; in any event it would be dangerous, and in the case of a slow-moving cyclone it might readily lead the vessel directly into the core of the hurricane. This is known to have been the case in many instances, and vessels have thus been drawn into the inner whirls of hurricanes and kept there for several days, making one or more complete revolutions around the center before they could extricate themselves. In fact, they might never have gotten out, if the storm itself had not moved off and left them.

The first of the accompanying plates, entitled,

WESTINDIANHURRICANES, AND OTHERNORTHATLANTICSTORMS,

gives a brief and yet complete résumé of what is perhaps the best modern practice. In these brief statements the attempt has been made to put concisely, intelligibly, andcompletely(if one will but read each and every sentence as carefully as they were written), the very latest, most important, and best-established facts, with which every navigator should be familiar. The paragraph entitled "Intensified trade-wind belt," for instance, is very important. A close consideration of the caution expressed in these few lines may prevent a serious mistake that might be made by a too rigid adherence to the old rules. The idea is as follows: It has been proved by Meldrum, from his studies of Mauritius hurricanes, that the SE. trade-winds blow toward a part of thetrackof a hurricane, rather than at right angles to the direction of its center, and it is therefore unsafe to assume that the center bears at right angles to the wind, or that, because the trade wind increases in strength without any decided change of direction, the center is approaching directly toward the vessel. This principle might naturally be expected to hold for similar storms in other regions, and Abercromby, in a thorough study of the whole subject, has shown that such is the case, although he states that "the position of this belt [of intensified trades] differs in every hurricane region, so that a special set of rules are necessary for each country." It seems to me, I must say, that in the absence of such special rules the law may safely be assumed to be general; its importance to navigators is certainly very great, and its principal effect must be to urge the greatest caution in making any attempt to cross the track of a hurricane, from the dangerous to the navigable semicircle.

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From the Pilot Chart of the North Atlantic Ocean, August, 1889, with Additional Paragraphs.

Explanation.—These diagrams are for practical use in West Indian hurricanes. The upper one will also answer for ordinary storms along the transatlantic route. The small arrows fly with the wind, the direction being stated at the end of each dotted line; the long arrow on each diagram is theSTORM TRACK, that is, the probable path of the cyclone through the belt of latitude to which the diagram applies.

Use of the Diagrams.—When a falling barometer, freshening rain squalls, &c., indicate a hurricane, select the proper diagram (according to theMONTHandLATITUDE), plot your position upon it by means of the direction of the wind, and thus ascertain the approximate bearing of the storm center. The probable storm track is indicated by the long arrow. If the wind shift, plot your position by means of the new wind-direction (nearer the center if the wind has freshened and the barometer has fallen). In this way you can readily observe every change of position relative to the storm center, and decide what action to take, according to the character of your vessel, the lay of the land, &c. These storms vary greatly in size, but are smallest and most violent in the tropics, where the cloud ring averages about 500 miles in diameter and the region of stormy winds 300 miles, or even less. You can therefore only roughly estimate theDISTANCEof the center, although itsBEARINGcan be obtained from the diagrams with a high degree of probability. There is also considerable variation in the direction of motion and the velocity of the storm along its track, but the general tendency is as stated herewith.

Cyclonic Circulation.—One of the most important indications that an approaching storm is of hurricane violence is the marked cyclonic circulation of the wind, lower and upper clouds, etc. This may be easily appreciated by remembering that a cyclone of any great intensity is an ascending spiral whirl, with a rotary motion (in the Northern Hemisphere) against the hands of a watch, as shown on the diagrams. The surface wind, therefore, blows spirally inward (notcircularly, except very near the center); the next upper current (carrying the low scud and rain clouds), in almost an exact circle about the center; the next higher current (the high cumulus), in an outward spiral—and so on, up to the highest cirrus clouds, which radiate directly outward. The angle of divergence between the successive currents is almost exactly two points of the compass. Ordinarily, with a surface wind from N., for instance, the low clouds come from N., also; on the edge of a hurricane, however, they come from N NE.,invariably. In rear of a hurricane, the wind blows more nearly inward; with a SE. wind, for instance, the center will bear about W., the low clouds coming from S SE. (two points to the right of the wind), etc. Great activity of movement of the upper clouds, while the storm is still distant, indicates that the hurricane is of great violence. If the cirrus plumes that radiate from the distant storm are faint and opalescent in tint, fading gradually behind a slowly thickening haze or veil, the approaching storm is an old one of large area; if of snowy whiteness, projected against a clear blue sky, it is a young cyclone of small area but great intensity.

Intensified Trade-wind Belt.—Another very important fact (established by Meldrum, at Mauritius) may be stated thus: When a hurricane is moving along the equatorial limits of a trade-wind region, there is a belt of intensified trades to windward of its track: not until the barometer has fallen about six-tenths of an inch it is safe to assume that, because the trade-wind increases in force and remains steady in direction, you are on the track of the storm. By attempting too early to cross its track, running free as soon as the wind begins to freshen, you are liable to plunge directly into the vortex of the hurricane.

General Information.—Hurricanes are especially liable to be encountered from July to October, inclusive, in the tropics (north of the 10th parallel), the Gulf of Mexico, and Gulf Stream region. Earliest indications: Barometer above the normal, with cool, very clear, pleasant weather; a long, low, ocean swell from the direction of the distant storm; light, feathery cirrus clouds, radiating from a point on the horizon where a whitish arc indicates the bearing of the center. Unmistakable signs: Falling barometer; halos about the sun and moon; increasing ocean swell; hot, moist weather, with light variable winds; deep red and violet tints at dawn and sunset; a heavy, mountainous cloud bank on the distant horizon; barometer falling more rapidly, with passing rain squalls.

Brief Rules for Action.—If the squalls freshen without any shift of wind, you are on the storm track: run off with the wind on the starboard quarter and keep your compass course (see caution in paragraph entitled "Intensified Trade-wind Belt"). If the wind shift to the right, you are to the right of the storm track: put the ship on the starboard tack and make as much headway as possible, until obliged to lie-to. If the wind shift to the left, you are to the left of the storm track: bring the wind on the starboard quarter and keep your compass course; if obliged to lie-to, do so on the port tack. In scudding, always keep the wind well on the starboard quarter, in order to run out of the storm. Always lie-to on the coming-up tack. Use oil to prevent heavy seas from breaking on board.

The next plate,

THEHURRICANE OFNOVEMBER 25, 1888,

is a very instructive illustration of an actual hurricane, and one of the most severe on record off our Atlantic coast. The spiral lines have been added to bring out conspicuously the wind-circulation, and several features will at once attract attention: the elongated shape of the storm, along a north and south line (the direction of motion); the wide region where there is a southeasterly gale (exactly analogous to the belt of intensified trades); the long sweep of northeasterly winds along the coast; and the marked variation from a strictly circular whirl. The right-hand side is the dangerous semicircle, and it is here that the navigator is called upon to decide whether he shall dare make the attempt to run before the wind and cross the track of the storm; the left-hand side is the navigable semicircle,—not verynavigablein this particular case, we may well believe, with no sea-room to the westward, a fearful N NE. gale, and a terrific sea. This is a case where every resource of seamanship and navigation may fail to save a ship, as the loss of the steamship "Samana" and a dozen other strong vessels, with all on board, bears sad testimony. Let me quote a few lines from a thrilling report by Captain Drew, of the American ship "Sea Witch" (this vessel's position is plotted on the chart about lat. 32° N., long. 75° W.): "Nov. 24: Hurricane from NE.; our position a perilous one, the ship rolling heavily and filling the decks with water; an awful gale, the worst we have ever had,—how will it end? At 3P.M., the sun out a moment through the thick sky. Nov. 25: Still blowing a hurricane, with awful squalls of rain; the seventh day of the gale. No side-lights can burn; the binnacle-light goes out as fast as we can light it. One blast from the north blew our brand-new lower-maintopsail away like brown paper. We performed the critical manoeuver of wearing ship, which saved the vessel: we were foundering." Verily, this was "out of the jaws of death," and probably there were few more sincere thanksgiving services than those held on board this vessel on Nov. 29th, 1888, as recorded in her log. One other report may be referred to here, as it is of especial interest. It is from the British steamship "Effective," whose position is plotted about half way between Bermuda and New York. At this time the wind was S SE., force 8, and the storm center was moving directly toward her. We learn from Captain Crosby's report that by noon, local time, the wind was strong from south; at 4:30P.M., a hard gale from east, moderating until midnight, barometer falling very rapidly. Nov. 26th, very heavy gale from NE., ship heading bow to sea; noon, wind east, barometer 28.60; 5P.M., wind N NE., 28.20; 10P.M., SW.; midnight, W., 28.20. This report illustrates the experience of a vessel close to the line of sudden shift of wind from SE. to N NE., and sustains very well the spiral lines drawn on the chart, just where there is an absence of data on the chart itself.

THEHURRICANESEASON.—June may be fairly said to be the first of the five hurricane months in the North Atlantic, and the above diagram is presented in order to call special attention to the Law of Storms, especially to certain important modifications of the old laws. The spiral lines indicate the general wind-circulation in this particular hurricane, and the complete data presented on the Chart must convince any one that conclusions based upon such evidence must be worthy of the most careful consideration. This hurricane was one of the most severe on record off our Atlantic coast, and, though much larger than a hurricane in the tropics, similar evidence can be presented to show that the 8-point rule is seldom a safe guide for obtaining the bearing of the center; a 10-point or even a 12-point rule is generally better, although the 8-point rule is fairly correct if applied to the direction of the low clouds, rather than the wind. The long sweep of NE'ly winds along the coast, when there is a hurricane below Hatteras, is a very characteristic and important feature. With a NE'ly wind off Block Island, for instance, it should not be assumed that the center bears SE.: the Chart shows that it may be almost due south. There is likewise a wide region where the wind is from the SE., and a vessel running before this steady SE. wind would plunge deeper and deeper into the hurricane. Similarly in the trades, to windward of the track of a hurricane: not until the barometer has fallen about 6-tenths of an inch is it safe to assume that, because the trade-wind increases in force and remains steady in direction, you are on the track of the storm; by attempting too early to cross its track, running free as soon as the wind begins to freshen, you are liable to plunge directly into the vortex.

Lack of space does not allow of further details, and I must go on to the next plate,

THEST. THOMAS-HATTERASHURRICANE OFSEPT. 3–12, 1889.

This plate is copied exactly from a Supplement issued with the Pilot Chart for October, 1889 (published Sept. 27th), with only the addition of the tracks of the two storms (as indicated by later data) and the tracks of a few vessels (see small charts dated Sept. 3, 4–7, 10). Considering the early date of publication, the wide expanse of ocean covered by the charts, and their essential accuracy (as indicated by later data), it must be acknowledged, I think, by anyone who is at all acquainted with the difficulties incident to this sort of work, that this supplement to the Pilot Chart hit more closely to the truth in this matter than would probably be possible under similar circumstances in one case out of ten. Had later data materially modified conclusions drawn at such an early date, it could not have been a matter of surprise, although this prompt publication would still have served a most valuable purpose in interesting navigators to contribute data likely to help us in establishing the facts. Indeed, the following quotations from the Pilot Chart and Supplement illustrate exactly what was desired, and what was actually accomplished by this publication: "This preliminary publication, issued two weeks after the storm reached our coast, well illustrates the cordial support this office receives from masters of vessels in its efforts to collect and utilize data regarding marine meteorology. It is desired to collect as complete data as possible regarding this storm, in order to publish a final report, and the present publication will be useful as a good working basis for a more complete detailed study of the hurricane." Also, "Special attention is called to the fact that this preliminary publication is only intended to give a brief outline of the facts as indicated by data received up to date of publication." Moreover, the name, nationality, and rig of every vessel whose report had been received in time to be used was published, and every statement made in the accompanying text was based on an exhaustive study of all the data.

It is interesting to note how slightly the very complete data now at hand have modified this hastily-prepared history, and all the circumstances urge similar quick work and prompt publication in every case, before other storms and other conditions have dulled public interest and directed attention elsewhere. The track of the easternmost of the two storms, as plotted on the first little chart, shows that it moved more rapidly than was anticipated, and recurved farther north: the fact is, its very existence was not even suspected tilltwo hoursbefore the final draft of the maps was made, and then only because the German steamship "Savona," from Baltimore for Brazil, suffered such damage from the hurricane on Sept. 5th (see chart dated Sept. 3rd for position) that she was obliged to run in to St. Thomas for repairs, and our consul, Mr. M. A. Turner, forwarded her report by the first steamer to New York. The following is a brief extract from this report, beginning at 10P.M., Sept. 4th: "Full hurricane, ship lying in trough of sea, laboring heavily and shipping much water. Cargo shifted; jettisoned 600 barrels of flour and 60 tons of coal. Broke steam steering gear and wheel, found rudder adrift, 3 feet of water in the hold, foundations of engines seriously loose and getting worse. Bore up for St. Thomas."

It is impossible, in the space at my disposal, to refer even briefly to the reports of the few vessels whose tracks are plotted on the charts: the stanch steamship "Earnmoor," foundering in the heart of the hurricane on Sept. 5th, eleven of her crew of thirty escaping in an open boat, and of these only seven surviving that fearful drift of twenty-three days; the "Sépet," between the two storms and escaping both; the "Lassell," from the tropics to Block Island, all the way in the grasp of the hurricane, without a sight of sun, moon, or stars, to fix her position; the "Ada Bailey," rolling in the long swell off Hatteras and watching the early indications of the approaching storm for nearly a week before it struck her; the "Hernan Cortes," forced to stand off into fearful danger by the still greater danger of a lee-shore at Hatteras; and the "City of New York," "Teutonic," and "City of Rome," starting on their Titanic race from Liverpool for New York the day after this great hurricane swept past St. Thomas, and reaching their goal with it, and in spite of all its fury. I must dismiss this whole interesting history with the following abstract of the report of Capt. Simmons, of the British brigantine "Victoria," whose original report is brief and to the point, like all the rest (see track of the "Victoria," northwest from St. Thomas, on the first small chart):

I passed through the cyclone, resulting in the total loss of the spars, sails, etc., of my vessel. The SE. sea became so heavy that I was obliged to heave-to. The sky was one sheet of dark gray, at times approaching black. The lightning was excessive only during the latter part of the storm; it appeared as a continuous quivering sheet around a great part of the horizon, extending about 10° above it and lasting many seconds, unaccompanied by thunder; the compass could not be read, the card spinning so that the points were indistinguishable. The lowest barometer reading was 27.86 (aneroid, corrected by comparison at Boston shortly before and at Halifax the following month).

The importance to navigators of a true appreciation of the law of storms—not the mere memorization of a set of rules, but an intelligent comprehension of the subject—is now perhaps clearly evident to the reader: at any rate, that is the object I have aimed at, rather than a mere formal statement of generally accepted principles and an abstruse discussion of isobars and gradients.

It will be seen thatthe probable bearing of the center, as indicated by the direction of the wind at a single station, is the great question, so far as the navigator is concerned. There are men who want and must have a hard-and-fast rule,—an 8-point, a 10-point, or a 12-point rule—something to act on without thought, while every nerve is strained to save the ship's spars, sails, boats, engines, and cargo, from damage or destruction. Under such circumstances, I think that perhaps the safest general plan is to use the old 8-point rule, butapplied to the low clouds, instead of to the wind. This is equivalent, generally speaking, to a 10-point rule, applied to the wind. That any such rule, if intended for general application, is only roughly approximate, goes without saying, or ought to do so, at least. The angle of bearing changes in different parts of the storm, it varies with the quadrant, with the latitude, with different storms, and with various other conditions, too numerous to be mentioned or even wholly known. One good general rule is that in rear of a hurricane the wind blows somewhat decidedly toward it; and yet that there are marked exceptions is well illustrated by the chart of the hurricane of November 25, 1888, already referred to. As a good example of the wind circulation in a hurricane in the tropics the accompanying diagram is of interest. This represents two days (the 3d and 5th) of the great Cuban hurricane of September, 1888, the intervening day (September 4th) being omitted, for the sake of clearness. Its severity is sufficiently indicated by the fact that it caused the loss of fully a thousand lives in Cuba, and destroyed property of the estimated value of $5,000,000 in the single province of Sagua. Now take any point on any one of these spiral lines, and observe the bearing of the center: in rear of the storm, especially, the 8-point rule is hardly applicable, and action based upon it might result disastrously.

The next and last plate, entitled,

HURRICANES IN THENORTHATLANTIC.—TYPICALCIRCULATION OF THEWIND,FROMACTUALOBSERVATION,

gives a still more complete illustration of the wind-circulation in hurricanes, with a brief discussion of the application of the 8-point rule. Especial attention is called to the statement made thereon (referring, of course, to hurricanes in the North Atlantic, but no doubt true for the entire Northern Hemisphere) that

"although the 8-point rule is nearly true when the wind is anywhere from north to south by way of west (that is, generally speaking, in the navigable semicircle), it is liable to be a very poor guide when the wind is from any point in the first or second quadrant."

Also to the following, which is applicable to the Southern Hemisphere by the substitution of "to the left" for "to the right:"

"Perhaps the best general rule is that the center bears about eight points to the right of the direction from which the low clouds come, or, what is practically the same thing, eight points to the right of the wind at the moment of a sudden shift in a heavy squall; after such a shift the wind will remain steady in direction for a time, but the center is meanwhile moving along and the angle of bearing changes until the next shift, when it goes again to eight points, and so on."

Such diagrams, carefully prepared from complete and reliable data, are of far greater practical value to navigators than volumes of explanation: they appeal to the eye and will live in memory long after ideas conveyed by printed words have been forgotten.

The above diagrams have been prepared from a large number of observations in order to illustrate the actual circulation of the wind in hurricanes, as a practical guide for navigators during the present hurricane season. The small chart that was presented on the Pilot Chart last month gave all the observations upon which the spiral lines were based for that particular hurricane (Nov. 25, 1888), and the same method has been followed here, only the observations themselves are omitted, for the sake of clearness. Perhaps the most important point to notice is that the surface wind blows in an inward spiral curve, and not circularly, except very near the center. The center therefore generally bears more than eight points to the right of the wind. Another very important point is the fact that although the 8-point rule is nearly true when the wind is anywhere fromNorth to South by way of West(that is, generally speaking, in the navigable semicircle), it is liable to be a very poor guide when the wind is from any point in the first or second quadrant. With the wind from NE., for instance, the center may bear anywhere from South to SE.; with the wind East it may bear from SW. to South; and with the wind SE. it may bear SW., West, or even (in the tropics) W NW. Perhaps the best general rule is that the center bears about eight points to the right of the direction from which the low clouds come, or, what is practically the same thing, eight points to the right of the wind at the moment of a sudden shift in a heavy squall; after such a shift the wind will remain steady in direction for a time, but the center is meanwhile moving along and the angle of bearing changes until the next shift, when it goes again to eight points, and so on.

It will be noticed that the northernmost of these two hurricanes was moving very slowly during the two days selected for illustration: had it been moving faster, the in-draught (or departure from the circular direction) would no doubt have been somewhat less in advance and considerably greater in rear than what is indicated. It is exceptional also to find a storm in this region growing smaller, as this seems to have done on Sept. 10th; it died out altogether in a few days, instead of continuing its motion toward E NE., as is usually the case. In the tropics the usual progressive motion is about W. by N., and this, together with the steady increase in size, is well illustrated in the case of the Cuban hurricane; it should be noted, however, that the interval is here two days, and not one, as in the upper diagram.

Masters of vessels are earnestly requested to keep regular observations for this Office during the hurricane season, even if only position, wind, weather, and barometer, at noon, G. M. T., are noted. A single additional report often adds greatly to the completeness of the data used in preparing these diagrams.

Finally, let us look for a moment at two sketches that I have made to give a graphic and I hope not incorrect idea of the cloud formation and the internal structure of a hurricane. In both sketches the vertical scale is of course greatly exaggerated. The first illustrates particularly the great cloud bank (with the "bull's eye," or clear central space, shown in cross-section); the storm-wave or general elevation of the surface of the ocean caused by the spirally in-blowing winds and low barometric pressure (the cause, oftentimes, of fearful floods along low-lying coasts); and the probable, or possible, circulation of the upper atmosphere over the whirl, together with the direct and reflected rays of a vertical sun as they pour into the central calm. The second sketch is to aid a clear mental conception of the actual motions of the particles of air as they flow inward below, whirl about the central core and flow outward above; this may help to free the mind from an erroneous idea that may be suggested by thinking of or seeing the enormous, piled-up, apparently stationary mass that constitutes thebarra, or cloud-bank of the hurricane, but which is really only the stationary and visiblelocuswhere the conditions are such that the whirling, rushing masses of humid atmosphere condense their tons of aqueous vapor and leave it, as they pass upward and outward. It is analogous to the cloud-cap, or banner, that hangs stationary over a lofty mountain peak, although if you visit the peak you may there find a living gale of wind.

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