CYCLONE, Hurricane, White squall, Typhoon. Tufan, . ARAB., HIND. I Tmvado, . . . . PORT. Ta-fung, . . . . CHIN. Tornado, SP.
Cyclone is the term now applied to the furious tempests formerly called taifun, typhoon, or hurri cane, because of their being uniformly found to be whirlwinds, and from the Arabic Touf, circumam bulation. Cyclones are of frequent occurrence from 109 miles N. to 120 miles S. of Madras, and between 1746 and 1881, 17 disastrous cyclones have been recorded. The first written notice is from the pen of Colonel Capper, a Madras officer, who describes them as whirlwinds of immense size, not less in diameter than 120 miles, and having their vortex near Madras or Pulicat. Other authors have followed since that date, 1801, offering theories and explanations of the phenomena,—Redfield and Espy in America ; Dr. Thom, 86th Regiment ; in Mauritius, Messrs. Bousquet, Hare, and Dove, Colonel Reid, Mr. Piddington of Calcutta, and many others. But, from the data furnished by their writings, it was left for Colonel Reid to form the law by which practical action has been given, and his position has been greatly extended and made easy by the intelligent labours of Mr. Piddington. The usual names, tempest, gale, hurricane, typhoon, being calculated to lead to confusion, a new term was sought for storms coming under the new law, and the word cyclone was selected, derived from the Greek Knklos, as neither affirming the circle to be a true one, though a circuit be complete, yet expressing sufficiently the tendency to circular motion in these meteors. Colonel Capper put forward the view that the stones of the Indian Ocean were rotatory. Mr. Redfield and Professor Dove further developed that theory ; and Colonel Reid discovered the fact that the rotation of these storms in the N. hemisphere was N.W. to S.E., or opposite to the direction of motion of the hands of a vvatch with its face upwards, and that the reverse is the case in the S. hemisphere. Mr. Espy of Philadelphia ascertained that in cyclones there is an indraught or centripetal force ; and Professor Dove explained the opposite direction of rotation in the northern and southern hemispheres, by what he called the law of gyration.
The subsequent writers on cyclones and their laws, have been Professor Taylor, Sir John Her schel, Mr. Blanford of Calcutta, Mr. Meldrum of
Mauritius, and Mr. Willson. Professor Taylor's theory was that cyclones originate from an upward expansion of the air, produced by local heat; that this is followed by an indraught of air, and that tbe rotatory motion of the earth produces spiral movement round a centre, over which a continu ous upward movement of the air takes place. This theory was adopted by Sir John Herschel in his work on meteorology. Messrs. Meldrum and Willson are of opinion that they are primarily due to lateral and opposite currents of air. Mr. Blau ford ascribes their cause to a local atmospheric depression arising from condensation of vapour, and so causing an indraught of air to the place of origin. Mr. Elliot favours a modified form of Mr. Blanford's theory (Geog. Mag., June 1877). Mr. Blanford's theory is in accordafice with the present views of the London Meteoroldgical Office, viz. that the winds blow from all qukters into every central area of lowest barometrical pressure. The workers and their contributions to this sub ject have been numerous.
From 1839 to 1851 Henry Piddington of Calcutta contributed lar'gely to the history of hurricanes ; and it was he who discovered that in India to the north of the equator they are circular, moving from right to left, and are pro gressive, and he made out the tracts on which they move, and their rates. Captain Carless and Dr. Thour, 86th Foot, gave an account of the great hurricane of April 1847, in which the Cleopatra, Captain Young, was lost.
Dr. George Buist collected accounts of hurri canes on the west coasts of India from 1647 to 1859, and wrote careful memoirs on the subject of cyclones. Lieutenant Fergusson published an account of the cyclone of 1862. Mr. Franklin, at Madras, published an account of the storms of 20th October and 25th November 1846, with diagrams. Lieutenants Mullins and Hemery described the cyclone at More and Cuddapah of 2d November 1847. An account of the Cal cutta cyclone of 1864 was drawn up by Colonel Gastrel and Mr. II. F. Blanford, with a list of recorded storms in the Bay of Bengal, from 1737 to 1865.