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ART. II.-Researches on the Gale and Hurricane in the Bay of Bengal on the 3rd, 4th, and 5th of June, 1839; with reference to the Theory of the Law of Storms in India. By HENRY PIDDINGTON.
That the hurricane part of the tempest which we are considering was blowing in tolerably well defined circles, has been, I think, clearly shewn in the foregoing part of this memoir. The object of this second part, is to adduce evidence, which shews that it was at the same time both a gale, i. e. a strong wind blowing in with tolerable steadiness from one quarter of the compass; and a hurricane, namely, a violent wind blowing in a circle or vortex of greater or less diameter. At present too it seems probable, from the dates, that the gale produced the hurricane. We may consider that this storm was one of those which usually occur at the change of the moonsoon from NE. to SW., which in various parts of the Bay may be said to take place between the 15th May and 15th June. It is from the 1st to the 15th June that we look for the rains in Calcutta, though sometimes, as in this year, they may be said to have begun in April. It will be borne in mind then, that whatever follows, whether facts or hypotheses, relates only to the beginning of the SW. monsoon. Future observations will inform us, whether the October Gales as they are called,-though they sometimes occur in November, are subject to the same or different laws. (The European reader will recollect, that October is the epoch at which the NE. monsoon takes the place of the SW. one.)
If we look at the Bay of Bengal, Map No. II, we shall be struck with the fact, that while it is bounded on the East by the mountain range which stretches from the Malay peninsula to Bootan, often approaching very near the shores, and rising to the height of from 3000 to perhaps 5000 feet on the Arracan coast; it is also bounded, on the West, by the Coromandel range, which supports the Eastern side of the elevated table lands of the Deccan. At the valley of the Mahanuddee (the river of Cuttack) however, at its junction with the Vindiya range, it turns suddenly to the North-Westward and Westward, leaving thus between it and the mountains of Arracan, the wide opening from Point Palmiras to Chittagong, which, to use an orientalism, is the gate to the plains of Bengal.
The salient angle, formed by the corner where the Vindiya and Coromandel ranges meet, and the entering one, where the Bootan, or Himalaya, and Arracan and Cachar ranges join (leaving however the valley of Assam as an opening for the great Burrumpooter to flow through,) thus form, as it were, an angular channel; through which all the lower strata of the current of the SW. monsoon may be supposed to find their way over the plains of Bengal and up the valley of the Ganges; and this is their natural course. But we may suppose that the SW. monsoon when urged to any great force at the mouth of the Bay, about Ceylon, must strike against the mountain ranges of Arracan in about from lat. 16°, which is that of Cape Negrais, to lat. 20° or 21°; or about that of Arracan; and, being deflected thence, must turn off in a paraboloidal line towards the great opening offered by the low lands at the head of the Bay, and thence proceed up the valley of the Ganges as before.
But when the head of the Gale is thus deflected, it may meet also with that portion of the monsoon which has blown along the Coromandel range and coast-called the "long-shore wind," by the old navigators -which has a much shorter distance to travel; and there occasion an eddy of variable winds, whirlwind or hurricane, according to the force of the first impulse-and this again influenced too, doubtless, by many causes to which we are yet strangers.
If this theory be true for these tempests, we should look to find points, about the meeting of the two currents, varying in position according to their respective forces, at which, during these gales, it should be comparatively calm, or blowing but moderately; and it is curious that at Balasore, in latitude 21° 28′, and at the Black Pagoda in 19° 62′ N. this comparative calm is found to have existed. My authority for this is the following letter.
Balasore, July 31st, 1839. DEAR SIR,-I should have been much at your service in giving you all the requisite information concerning the gale here, had any taken place, but we had only strong gusts of wind at NE. to SE. with uncommon heavy rain on the 5th, 6th, and part of the 7th of June, which even to this day has kept back the rice crops. The thermometer fell to 8140, and unluckily my barometer was broken a few days prior, so that we could only foretel a gale coming on by the blackness of the heavens to the Eastward; which gale did not reach from the Northward of Point Palmiras to Balasore, but blew hard from Point Palmiras to below Pooree to the Southward. No vessels were lost in the Balasore roads; but to the Eastward they may have been lost, as a Telingah topgallant mast was picked up, besides pieces of deal boxes, supposed to have contained glass-ware, marked "Protector," which vessel was lost to the Eastward, between the reefs, last October.
Gales at Kedgeree, though blowing dead to windward of us, distant seventy-five miles, do not always reach this coast; as in the May Hurricane of 1833, when the "Duke of York" was blown from her moorings at Saugor across to Hidgelee, and became a wreck, yet the gale did not reach here, although the bank to the Eastward in the heavens so plainly indicated a gale, that every person here barred up their doors and nailed them. We only had a good topgal
The Neilgherry Hills appear to influence the winds much on the coast north of Point Palmiras, as the winds are generally throughout the SW. monsoon, SW. to W. in the morning to 7 A. M., veering round to S. and SE. P. M.; and in the NE. monsoon, W. to NW. veering round to NE. after 8 A. M.
Mr. Richardson, Branch Pilot, informs me, moreover, that during the fury of the Gale of 1833, in which the "Duke of York" was wrecked, and he himself was driving about with all his anchors down, some passengers whom he had previously landed at the Black Pagoda were upon the top of it, and felt no excessively violent wind, though they saw the horizon very black, and the sea dreadfully agitated to the North Westward of them.
The slow rate at which our vortices travel onwards is very remarkable, but seems, if future observation should confirm it, to afford countenance to this theory; for, as before said, we may consider them as pent up between the current passing round the vortex of the parabola and the Coromandel range; and no doubt to feel, as water in similar channels would do, the repulsion from these last. It is clear, as shewn in p. 576, by the log of the "Indian Oak," that the monsoon was blowing up along the coast as far as Vizagapatam, from between which and Gan
jam, to Point Palmiras, the Hurricane was probably felt. Its limit to the North we well know to have been between Point Palmiras and Balasore, but I could obtain no intelligence from Ganjam to fix a limit to the South.
We should also find that, as the current of air proceeds up the valley of the Ganges to the North Westward, it should give rise to an Easterly Gale, which has also in this instance occurred, as will be seen by the following extracts, the first being from a very able and interesting letter from Mr. Ravenshaw, of the Civil Service, dated Chuprah in Behar, lat. 25° 46′ N. long. 84° 46′ E.
Chuprah, July 17th, 1839. DEAR SIR,-Having observed in the Newspapers that you are desirous of obtaining information connected with the Gale which occurred in the Bay of Bengal from the 3rd to the 5th June inclusive, I have the pleasure to contribute my mite to the stock of facts which you are engaged in collecting. The enclosed extract from my Register will shew the height of the Bar. and Ther. at 10 A. M. during the Gale, and for some days succeeding it. I regret that my official duties prevented me from taking observations at 4 P. M.; but I hope the small amount of information afforded will not be without use, in shewing the direction and duration of the Gale of this district, inland from the Bay of Bengal. It will be remarked, that the Gale did not commence here until the 4th instead of the 3rd June, and that it terminated on the 7th instead of the 5th. The Bar. kept falling during the continuance of the Gale, and strange to say did not reach its minimum until the day after the violence of the Gale had ceased, i. e. the 8th. The direction of the Gale was nearly due East, but on the 8th the wind shifted to the SW. and West, and on the 9th blew as furiously from the latter quarter as it had previously done from the East; towards evening, however, it shifted to the NE. On the 10th it changed to SE., on the 11th to SW.; and the following day to the West. On the 14th and 15th it again veered to the NE. and EbN. until on the 16th it resumed its old position of East, which is the usual direction from which it blows at this season of the year. From the above it would appear that the wind, after the violence of the Gale had subsided, acquired a rotatory motion and turned twice round the compass in a Southerly direction before it recovered its equilibrium. By letters received at the time from Mootebarry, 60 miles North of Chuprah, and from Gyah, about 90 miles South of this station, I learnt that the Gale occurred with equal violence at those places. The breadth of the column of air put in motion was therefore at least 150 miles, and probably much greater. It would be interesting to ascertain the exact limits of this Gale inland as well as at sea, which object might be effected by your addressing a circular letter to the residents at each of the principal stations in the Western Provinces e. g. Allahabad, Cawnpore, Agra, Delhi and Saharunpore. In
formation from these points would probably give the extreme length to which the Gale extended, as information obtained from Jubbulpore, Gwalior, and Ajmere, would shew the extreme breadth. I do not recollect at present from what direction you stated the Gale to have blown in the Bay of Bengal, but if from the SW., the usual course of the monsoon, it is difficult to account for its blowing here from the East, unless we suppose the column of air to have been driven against the Assam and Himalaya Mountains, and by them turned in a Westerly course. In this event, it is probable that the Gale may have subsequently followed the direction of the mountains NW. perhaps as far as Hurd war.
I conclude that it is not your intention to confine your observations and inquiries to the Gale under consideration, but to all storms of magnitude in the Bay, or its vicinity. The Gale which seems to occur almost annually in the Bay of Bengal in the month of October, would, from its regular recurrence, form an excellent subject for observation. It was felt at Chuprah during the two years that I have been stationed here. On the first occasion it blew (to the best of my recollection) from the East, whereas last year it came from the West.
It appears to me very desirable that either Government or some public body like the Asiatic Society, should take measures for securing an uninterrupted official record, not only of the periodical and occasional storms which extend generally over large tracts of country, but also of local atmospherical peculiarities-the changes in the direction of winds and storms occasioned by mountains and the larger rivers also of the general character of the seasons in different parts of the country-the paucity or abundance of rain-the minimum rise of the Ganges, Burrumpooter, &c.-the price of grain as affected by the seasons-the date of the commencement and termination of the rains of the hot winds-or of any other prevailing winds.
The Asiatic Society through its numerous members might, I should imagine, without difficulty obtain information on the points adverted to from all the principal stations in India, which should be annually digested and published in their Journal. These again will be compared and generalized every 10 years or so by a Meteorological Committee of the Society. The Asiatic Societies of Madras and Bombay might be requested to adopt the same system throughout their respective Presidencies, so that the observations might embrace the whole of India. Such a combination of laborers in the cause, and the consequent accumulation of facts, assisted by the rapid progress of science in these days, would almost justify the hope that we may ultimately arrive at the discovery of some general laws by which the seasons are regulated; and by which we may be able to foresee and to guard against both inundation and famine, in a country where their ravages are often so destructive to life and property.