The Sailor's Pocket Book: a Collection of Practical Rules, Notes, and Tables

In all cases within the tropics, they commence to the eastward. For some days they travel along a path not exactly west, but inclining a point or two towards the pole of that hemisphere which they are crossing; and, as they advance, they seem to be more inclined to curve away from the equator. When they reach the 25th degree of latitude, they generally curve still more until they move to the N.E., in the northern hemisphere, and to the S. E. in the southern hemisphere. Occasionally they are found to cross the line of the shore, and to sweep over the land that opposes their progress, as appears to be generally the case in the East Indies and China Sea; but but by far the greater number seem to be repelled by the land, so as to be deflected back to the N.E. in the Northern hemisphere and to the S. E. on the other side of the equator. The Atlantic and Japan storms, for instance, almost always wheel round to the northward, and follow the sea-board of North America or Japan.

Another remarkable feature of these storms, is their increasing violence in the neighbourhood of their centre or vortex; and as this is approached (unless on the direct line of its own progressive motion), the more rapid become the changes of the wind, which at length, instead of veering point by point, as on entering the stormfield, now flies round at once to the opposite point.

With that threatening aspect of the sky which generally foretells bad weather, every seaman is acquainted; in addition to this a confused and troubled agitation of the sea often precedes these revolving storms, and always shows that they are at no great distance.* The best and surest of all warnings will, however, be found in the barometer; which, within the tropics varies so slightly under ordinary circumstances that any fall greater than 35 inches is a sure sign of an atmospheric disturbance; but in more temperate latitudes where the barometer varies considerably with no apparent atmospheric change, the indications are less certain. If these combined prognos-tics should occur within the limits of those regions which have been

* The Chinese boatmen of Hongkong frequently predict the approach of a Typhoon 24 hours before its commencement: they are seldom in error.

The Aneroid is of great value at such a time, especially at night, for it can be registered with great facility, and being portable, may be watched constantly,

pointed out, let the seaman immediately consider the possibility at least of his being about to encounter a storm of the revolving type.

The first care should be to discover the position of the storm with respect to the vessel. This is readily determined, by noting the direction of the wind at the commencement of the storm, as the bearing of the centre generally lies eight points of the compass from the direction of the wind. The rule is therefore: face the wind and take the eighth point to the RIGHT, that will be about the bearing to the centre of the storm if in north latitude; or if in south latitude, the eighth point to the LEFT. For example: suppose the vessel to be in 14° N. latitude, the wind from the North, and the barometer and sky indicating a coming gale,-then, look at the compass, take the eighth point to the right of North, and East will be the bearing of the vortex. Or, if in 14° S. latitude, with the wind South, take eight points to the left, and East will be the direction of the centre.

Knowing the bearing of the centre, it is next required to discover on which side of the storm's path the vessel lies. In the Northern Hemisphere if the ship is on the right-hand side of the path (looking in the direction towards which the storm is advancing) the wind veers N., N.E., E., S.E., or with the hands of a watch, whilst if she is on the left-hand side of the path, the wind veers N., N. W., W., S.W., or against the hands of a watch. And in like manner in the Southern Hemisphere, if the ship is on the right-hand side of the path (looking in the direction towards which the storm is advancing), the wind veers S., S.W., W., N. W., or with the hands of a watch, whilst if she is on the left-hand side of the path, the wind veers S., S. E., E., N.E., or against the hands of a watch.

In using the above rules it is essential that the ship's position be as nearly as possible stationary; for if a ship advance somewhat faster than, and in the same direction as, an approaching storm, having the wind also in the same direction (ship running), the wind may shift in a direction exactly opposite to that which would have

when the marine barometer may not be accessible; moreover, its variations occur simultaneously with their causes, showing minute changes, unobservable in the best constructed marine barometers, owing to the pumping of the quicksilver, when the motion of the ship is violent.

been observed had the vessel been stationary, and an erroneous conclusion as to her position in the storm would be drawn. The advisibility of heaving-to on the first approach of a hurricane, cannot therefore be too strongly urged.

Although a cyclone may be made use of by the experienced seaman when making a passage, and a good run frequently ensured; and, where sea room will admit, a vessel may be able to run out of the direct influence of the coming storm; yet, as a general rule, it is advisable to HEAVE THE VESSEL TO ON THE TACK ON WHICH SHE WOULD COME UP AS THE WIND SHIFTS; therefore, when the ship is in the right-hand semicircle, i.e., on the right-hand side of the storm's path, she should be hove-to on the starboard tack; and if in the lefthand semicircle, on the port tack.

If, with the ship hove-to, the wind continues steady in the same direction, increasing in violence with a rapidly falling barometer, it may be presumed that the ship lies in the direct path of the storm's centre, and it will be necessary to run before the wind.

If the vessel is unable, from want of sea room, to run, her position becomes one of great danger, and every precaution should be taken to prepare for the passage of the centre over the ship; for the steady wind will be succeeded by a short interval of calm, to be followed by a sudden and most violent burst of wind from the opposite point of the compass to that first experienced. After the calm the barometer will commence slowly to rise.

Caution. In the practical application of the theory of revolving storms, it must be borne in mind that, although the region and season of the year would render the seaman extremely cautious, yet every strong wind or gale met with, especially in extra tropical regions, must not be treated as cyclonic. For example: the master of a vessel running up the Bay of Bengal in the month of May, with a S. W. gale, heavy rain, and a falling barometer, must not at once assume that he is in a cyclone, the centre of which bears N. W., and therefore that a North or N.E. course will carry his vessel clear of danger.

Similarly, in the neighbourhood of Mauritius, in the months of January or February, with the wind from S. E., steady in the

direction, but increasing, accompanied with squalls, rain, and falling barometer-to assume that the vessel is in a hurricane, the centre of which bears N. E., and to run to the N. W., would be dangerous.

The barometer must, in these cases, be closely watched, and a decided fall of at least 3 inches from the normal average should be experienced before the conclusion is arrived at, that the vessel is within the influence of the cyclone proper.

In either of the above cases the safe proceeding is to heave to, and carefully watch for the shifting of the wind, and the changes of the barometer; then, if the ring of the former, and the marked fall of the latter prove the gale to be rotating, or cyclonic, the position of the centre and probable direction of its path, could be determined with some degree of precision.

The following Tables, taken from Professor Dove's "Law of Storms," gives in detail how a ship should be handled under any circumstances in these storms.

*Such a proceeding, in fact, proved fatal to several vessels which, under these circumstances, weighed from Reunion and stood to the N.W. in February, 1860. See "Notes on Cyclones in the Southern Ocean," by C. MELDRUM, M. A., F. R. A.S.