(a) The barometer always falls during the passage of the advancing semicircle of a revolving storm; and again (b) The barometer always rises during the passage of the receding semicircle of a revolving storm : hence, in cases of manoeuvring to take advantage of hurricane winds and to keep just within the verge of the storm, the barometer is of signal benefit; it should be kept as high as possible without losing the wind. When sailing from the vortex the barometer will rise; when sailing towards the vortex it will fall; and if, after having fallen considerably, it rises-at first rapidly, and then gradually—such rising indicates that the first (or dangerous) half of the storin has passed away. Beyond the tropics, and in the higher latitudes, the oscillations of the barometer are incessant and irregular, ranging (rising and falling) through a space of 1 to 2 inches, or even 3 inches on extraordinary occasions; and thus its indications fail at times to convey the same definite information that they do between the tropics, unless intrepreted by the aid of the thermometer and hygrometer, in conjunction with various atmospheric and oceanic appearances. Between the tropics the oscillations of the barometer are also incessant, but they are regular. The periodical range due to the season does not exceed a few tenths; but the most marked of the periodical oscillations, is that which occurs daily. It shows every day two maxima and two minima, as follows, according to the locality; at some time between 9 and 11 a.m. the mercury begins to fall, and continues to do so until between 3 to 5 p.m., when it reaches the lowest point of depression; it then rises until between 9 to 11 p.m., when it reaches the highest point of elevation; after that it re-commences to fall, falling until between 3 to 5 a.m., from which time it again rises until between 9 to 11 a.m. The amount of range, again according to locality, varies from .06 to .12 of an inch. Tack on which to heave-to.-When involved in a hurricane, in the Northern Hemisphere, if the ship is on the starboard tack her head is directed from the center; but if on the port tack, her head is towards the center. In the Southern Hemisphere, as a necessary consequence of the rotation of the wind, the conditions are reversed, and thus the starboard tack leads towards, and the port tack from, the center of the storm. But, nevertheless, as a general rule, since it is advisable to heave a ship to so that she shall come up as the wind shifts, the rule will be-in both hemispheres but (a) When in the right-hand semicircle heave-to on the starboard tack; (b) When in the left-hand semicircle heave-to on the port tack. Running is never recommended, except as a necessity, owing to the danger of broaching-to if the wind is brought on the quarter; but if compelled to do so (a) Keep the wind well on the starboard quarter in the northern hemisphere; (b) Keep the wind well on the port quarter in the southern hemis phere. Heaving to will always be more or less dangerous when in front of the cyclone and near the axis line, and having reason to believe that the ship is in that position, avoid having-to under the following circumstances, unless compelled to do so: When in the Northern Hemisphere Storm moving N.W.-ly, winds between N.N.E. and E.N.E. Storm recurving, winds between E.N.E and E.S.E. Storm moving N.E.-ly, winds between E.S. E. and S.S.E. Storm moving S.W.-ly, winds between S.S. E. and E.S.E. Storm moving S.E.-ly, winds between E.N. E. and N.N.E. General Rule.-The elder cyclonologists were very cautious about giving rules for manoeuvring. Their rules may be summarized as follows: Heave-to for the first hour or two (when overtaken by a cyclone) to determine your position in the storm, by noting the changes of wind and state of barometer; then, if it be deemed safe to stand on, do so; should bad weather increase, with a falling barometer, heave-to again, and so continue, until new changes indicate that standing on may once more be attempted ; if, having done so, there is no improvement, exercise your own judgment as to heaving-to a third time. PIDDINGTON was wise in his generation, but far too severe a critic, for it is often easy to see, after the event, how misadventure has occurred; but none of the cyclonologists ever wrote more practical directions than he did, when in later days he penned the following:-"ALL POSITIVE rules for manœuvring are sheer nonsense, and only tend to mislead; every ship in every cyclone must have its own peculiar management, dependent on the four great elements of the problem, which are—(1) the ship and her searoom; (2) the track of the cyclone; (3) its rate of traveling; and (4) the ship's run and drift; while on the part of the commander, caution and watchfulness are essentially requisite." The meteorological signs that herald the approach of, and that usually accompany, a hurricane or cyclone have been carefully collected from various sources, by Mr. W. R. BIRT, and a summary of them is given in his "Handbook of the Law of Storms." In enumerating and collating them he has classified them under several distinct and characteristic headings, as follows: Meteorological signs recognized by the feelings 1. A sultry, oppressive state of the atmosphere. Meteorological signs recognized by the eye 3. A remarkably clear state of the atmosphere, so that the stars may be seen to rise and set with nearly the same distinctness as the sun and moon. 4. A peculiar white appearance in the zenith, more or less of a circular form. 5. A remarkably red or fiery appearance of the sky. (This is not unfrequently of such intensity as to tinge all surrounding objects with a deep crimson; and when this is observed there can be no question that the violent portion of the cyclone is not far from the vessel. When this red light is seen at night, the impression on the seaman's mind is, that day has broken before its time.') 6. A peculiar coloring of the clouds, more especially of an olive green. (This is generally the precursor of a most violent and terrific hurricane.) 7. A thick, hazy appearance in that quarter of the horizon in which the cyclone is raging. 66 8. A remarkable and peculiar appearance of the heavenly bodies. When shining through a haze, they are said to shine with a pale, sickly light, and are not unfrequently surrounded by rings of light, or halos. Some observers describe the stars as 'looking big, with burrs about them.' Others speak of their dancing, and generally they have been noticed as being remarkably bright and twinkling. 9. The sun on some occasions has exhibited a blue appearance, and white objects have been seen of a decided light-blue color. The sun has also been observed of a pale and somewhat similar appearance to that of the full moon. 10. A dense, heavy bank of cloud in the direction of the hurricane. 11. A peculiar appalling appearance in this bank, more particularly as if it were a solid wall drawing down upon and closing around the ship. 12. A darting forward of portions of this bank, as if torn into rags and shreds by some violent force, and driven before, not borne by, the wind. (When this indication is distinctly recognized, a run of about two hours towards the center will involve the vessel in a destructive hurricane.) 13. A peculiar motion exhibited by small bodies, as branches of trees, when agitated by the wind, consisting of a sort of whirling, not a bending forward, as if bent by a stream of air. 14. Lightning of a remarkably columnar character, shooting up in stalks from the horizon with a dull glare; also like flashes from a gun, and sparks from a flint and steel. Meteorological signs recognized by the ear— 15. A distant roar (probably of the hurricane itself), as of wind rushing through a hollow vault. 16. A peculiar moaning of the wind, indicative of the close proximity of the violent portion of the hurricane. "The meteorological phenomena accompanying a revolving storm may also be enumerated thus: 1. A very rapid motion of the air, constituting the hurricane, and increasing in velocity as the center is approached. 2. A fitful variation of intensity in the force of the wind, which sometimes blows with fearful violence, carrying away everything that opposes its progress, then sinking to a gentle breeze, or even lulling to a calm, but almost immediately afterwards springing up with greater violence than before. The hurricane winds are nearly, if not entirely, without exception puffy, violent, and blowing in gusts. 3 An immense condensation of aqueous vapor, forming large banks of cloud, which precipitate torrents of rain. The condensation appears to be so exceeding rapid that large quantities of electricity are generally developed, giving rise to incessant flashes of lightning. 4. A general darkness and gloominess within the area of the cyclone, relieved only by the fitful glare of the lightning, or the appearance of the imperfect circle of light near the center or axis of the storm. 5. A separation of the clouds in or near the center of the hurricane, so as to produce in the immediate neighborhood of the axis a clear sky, through which the sun and stars are often seen with great brilliancy. 6. A calm in the center of the cyclone. "Indications of approaching or existing hurricanes manifested by the ocean, of especial utility to vessels at anchor in roadsteads, &c. : 1. A swell produced by the storm-wave rolling in upon the shore, at first of a gentle character. The direction of this swell will pretty surely indicate the bearing of the storm, and its changes will point out, in some localities, the course the hurricane may be pursuing. 2. A swell rolling in, without changing its direction, may be regarded as indicative of a hurricane approaching the shore. The same phenomenon met with at sea (the ship's course being taken into account), will indicate the bearing down of the cyclone on the vessel. |