24 REPORT — 1867. 



Revolving storms, however, do not always take place on such occasions, altliough, 

 as the monsoon approaches, the wind generally veers from E.S.E. to East, North, 

 and N.W., with much rain, and generally thimder and lightning. Nor does the 

 monsoon always advance along its whole extent in longitude, but more frequently 

 penetrates into the trade-wind, and then only one rotatory storm is formed. When 

 the monsoon and trade-wind are in collision over a considerable extent of longi- 

 tude, or across the whole ocean, two or more revolving stomis may be formed, which 

 sometimes rage together for several days, as in the case of two violent hurricanes 

 which occurred between the 8th and the 17tli of Februarj', 1861, and of several 

 others between the 6th and 24th of April, 1866. On occasions like these as many 

 as five rotatory storms ha^'e been known to exist at the same time along the inner 

 borders of the two winds, but they did not all last long. 



In the earlier and latter parts of the season these storms often do not travel 

 beyond the parallel of 16° S. They are most frequent in February and March, and 

 during those months they generally advance to 25° S., and sometimes to 30° or 

 32° S. Their tracks are generally curves, the convexities of which are towards the 

 west, and the apices anywhere between the parallels of 14° and 24° S., according 

 to the season. It would appear that they traverse the trade-wind region in conse- 

 quence of the progress of the aqueous precipitation being in that direction, and of 

 the monsoon extending farther south on the western than on the eastern side of 

 the ocean, as already stated. The direction of the wind in the body of the storm 

 may be accounted for hj the relative positions and directions of the" monsoon and 

 trade-wind, independently of the earth's rotation on its axis, although that also 

 may have an effect. 



With regard to the form of these storms, it varies, and is not so circular as is usually 

 supposed. The wind generally blows spirally towards and ultimately around the 

 centre, as is shown, not only by the collective evidence of vessels on all sides of the 

 storm, but also by individual vessels occasionally running completely round the cen- 

 tre, and being gradually drawn into it. An example of this occun-ed in May, 1863, 

 when a vessel belonging to the port of Dundee, called the ' Earl of 1 )alhousie"' CCapt. 

 Campbell), scudded, at the rate of 10 to 13 knots an hour, three times round the 

 centre of a revolving storm, which at the time happened to be nearly stationan-, 

 till at length she reached the centi-al calm. (Charts were exhibited showing the 

 positions of the vessels and directions of the M-ind in this storm at noon on each 

 day from the 7th to the 20th of the month.) 



As the trade-wind in front of a revolving storm often blows in strong gales with 

 a falling barometer over many degrees in longitude, and the direction of the wind, 

 especially at a distance, is far from being at right angles to the bearing of the 

 centre, severe losses have occurred in consequence of vessels, having the wind at 

 S.E., running to the west or N.W. with the view of crossing the storm's path, 

 under the impression that the centre bore N.E. In place of bearing N.E., when 

 the wind is from S.E., the centre may bear North or N.N.W., and if the storm be 

 travelling to the S.W., as is often the case, a vessel steering westward or N.W. 

 may be running to her destruction. During a humcane in February, 1860, for 

 example, a number of vessels left the roadsteads of Reunion with the wind at 

 S.E., and, rmming to the N.W., got into the heart of the storm. Several of 

 them were wrecked on the coast of Madagascar, others were never heard of, and 

 of those that returned some had to be abandoned. The safest course seems to be 

 to lie to and watch the barometer and wind till the bearing of the centre be known 

 with some certainty. 



But perhaps the greatest losses of life and property in the Indian Ocean south of 

 the Equator arise fi-om homeward-bound vessels running into revolving storms to the 

 southward of them, by taking supposed advnntage of the N.E. winds of a storm, 

 between the parallels of 10° and 16° S., and steering to the S.W. till they get in 

 fi'ont of the storm. This is the more to be regretted, inasmuch as all such losses may 

 be easily avoided by lying-to till the barometer rises and the weather improves, or by 

 proceeding cautiously to the southward. Heavy losses occur annually from inat- 

 tention to this simple precaution. In May, 1863, for instance, of twelve liomeward- 

 bound vessels which had got involved in a revoh-ing storm by nnming to the 

 southward with increasing winds, falling barometer, and threatening weather, two 

 had to be abandoned at sea, and the others were so disabled that on arrivins' at 



