



WIND. 



WIN' IV 







on the 16th, off LUbon, there wen heavy gales from s.v. 

 All these circumstances indicate a ntonn revolving in the order N., W., 

 while it) centre advanced in a line nearly from south to north. 

 Professor Dove bos remarked, in his paper already referred to, that in 

 Pnisua all itormi are great whirlwind*, which continue during one or 

 several days, sometimes as many as twenty, the rotation of the wind 

 being generally in one direction. 



It resulted from the investigation and comparison of these and other 

 facts by Mr. ReoTield and Sir W. Keid, that a revolving storm, or 

 Cyclone, as it is called, rotates, in the Northern hemiH|>here, from the 

 vast, or the right hand, by the north, towards the west, or contrary 

 to the hands of a watch; and, in the Southern hemisphere, from 

 t he west, or the left baud, by the south, toward* the east, or <-,'//. 

 the bands of a natch. Professor Dove expresses the same fnct, 

 beginning in both cases with the right hand, or the east side of the 

 cyclone, by S., K., N., \V. for the Northern hemisphere, and N., I'.., s., 

 W. for the Southern. 



The variations in the height of the column of mercury in a baro- 

 meter afford, within the tropics, indications of the approach and the 

 state of a whirlwind ; the column is observed to fall gradually during 

 part of the time that the storm continues at a place, apparently till the 

 centre of the vortex has passed over, and then to rise as gradually. 

 The depression of the column continues also during the movement of 

 a storm from one region to another ; the centrifugal tendency of the 

 revolving particles probably opposing that of gravity, by which the 

 particles would otherwise move towards the axis of rotation. Proofs 

 of these circumstances .are given by Sir W. Keid from observations 

 made at Mauritius, during the hurricanes in March, 1S19, and in 

 February, 1 



As the investigation of the subject has proceeded, the observation of 

 the depression of the barometer during a revolving storm has been 

 found to be of the utmost importance, as well in a philosophical u.s in a 

 practical point of view. The fact is connected inseparably with the 

 general history of the atmosphere. That a considerable decrease of 

 pressure should be an effect of. any unusual disturbance in it is a 

 supposition BO natural, that it at once occurred to those who first 

 remarked that the weight of air surrounding us is not always the same. 

 For the purpo.se of measuring these changes, the inventor of the air- 

 pump, Otto Von Guerike attached a scale to the water barometer, 

 which he also invented, and he records an observation that in 1 1 

 1660, the index pointed below the lowest mark on the glass tube, on 

 which he hod confidently affirmed that there was a great storm some- 

 where, and that, two hours afterwards a tempest was raging in the 

 district of Magdeburg. As a more recent example, Dove mentions the 

 great storm of January 17, 1818, which extended from the shores of 

 Kugland to Metucl, and was felt throughout a region 240 German 

 miles in length, and during which the barometer fell eight lines in as 



many hours, having also fallen between the 3rd and the 17 

 January in all twenty-one lines, or an inch and three-quartern 

 experience of the lost two centuries indeed has so far confirm 

 remark of Yon (Juerike, that the scales attached to our ciiimu 

 lianmu tent usually terminate with " very stormy." But its 

 cability in not confined to the temperate zone: in lat. 7"' N 

 70 \V., tlie warning afforded by a considerable fall in the i 

 barometer, enabled the eelebrated navigator Scoresby t 

 dangers of a tempest which lasted two days uninterruptedly. Sir 

 W. Keid, as we have just aeeo, established corn-- tx in 



relation to the revolving storms of the Indian Ocean; and in the. 

 regions of the trade winds, and of the monsoons, the nun. 

 examples of greatly diminished pressure ushering in the typhoons 

 and \Sest India hurrir.n.s ore now well known. 



The ' Ijiw of Storms,' principally by the skilfully conducted and 

 continued researches of Mr. Kedfield and Sir \V. Keid. bavin/ 

 brought into the condition explained in the preceding columns, and t In- 

 latter, especially, having indicated to the seaman not only how ho 

 might, by applying the acquired knowledge of that law. avoid the 

 dangers of hurricanes, but even profit by their Intervention in his 

 Voyage, a new advance was given to the subject; a new ex i 

 added to those by whom it had been investigated, and who, indc 

 I', en pursuing hix own researches oantomporaoeouily with n>: 

 theirs. The late Mr. Henry Piddington, President of Marine Courts, 

 Calcutta, communicated to the A.- 1 of Bengal, in 18 



first of an extensive series nf memoirs, in which lie discussed the phe- 

 nomena of revolving storms in the Indian and Chinese Seas, as recorded 

 in the log-books of the ships which h.i.l exj -hem, and in 



various other documents. These having been first printed in the 

 'Journal 'of the .Society, Mr. Piddington published a valuable 

 of their results, and of those obtained by his contemporaries, in a work 

 entitled ' The Sailor's Horn-Book for the Law of Storms,' of 



edition- appeared, the first in ISIS and the second in 1851. 

 In the first edition of this work, the author proposed the designation 

 if ( 'i/rlone, from the Greek KmrAos, a circle, also the coil of a snake, 

 for hurricanes, typhoons, revolving storms, and circular blowing gales 

 in general, superseding, for nautical as well as scientific purposes, all 

 the terms previously in use. This designation having been uui 

 adopted, we shall employ it in the remainder of this article, premising, 

 however, that the term ' whirlstorm' has been recommended by some 

 as an apt English emphatic synonyme when required. 



Mr. Piddington constructed, and published in his work, what he 

 termed a barometrical chart, exhibiting certain nmr.erical phenomena 

 of seven cyclones, which, as being one of the most instruct i 

 , representations of physical facts we have ever - iiis inn v> h.it 



may be called vertical sections of the cyclones, we have copied in the 

 diagram annexed. 



A few words in explanation are required. The double set of num- 

 bers and spaces at the top line of the diagram, forms a general scale of 

 distances ill miles from the centre of each cyclone. Tin- double set at 

 tli- Imttom forms a scale of hours before and after the passage of the 



centre. The numbers and spaces at each side denote the heights of 

 the barometer in inches. The Roman numerals refer to : 

 enumerated in the following list, the barometrical observations taken 

 as standards being such an were mode on shore, which alone could be 



