The knowledge of the laws which regulate the movements of cyclones is of great practical importance to the mariner, since it points out to him the direction in which he has to steer in order to remove as soon as possible beyond the reach of danger, and thus the men whose patient investigations have traced the march of these tremendous storms, and pointed out the track they are forced to pursue, have not only rendered service to science, but rank highly among

the benefactors of mankind.

The origin of cyclones is in all probability due to the encounter of two currents of air moving in opposite directions. Thus the West Indian cyclones are most frequent between the months of August and October, when the heated shores of South America are beginning to attract towards them the colder air of North America. In the Indian and Chinese seas they generally take place at the change of the monsoons, when the conflicting masses of air loaded with electricity enter into a struggle for the mastery, and produce a rotatory movement round a neutral point as they come into collision, even as the Maelstrom is produced by the meeting of conflicting currents.

CHAPTER XIX.

THE SAINT ELMO'S FIRE.

Superstitious Notions of the Ancients-Castor and Pollux-Helena-The Phenomenon frequently mentioned by Ancient Historians-Columbus and Magellan-Admiral Forbin-Electrical Emission of Light on Branches-On the Summits of Mountains-Adventure of Professor Siemens on the Pyramid of Cheops-Electrical Aureolas-Luminous Rain-Luminous Dust-Causes of the St. Elmo's Fire and of the Analogous Phenomena.

BESIDES

ESIDES the discharges of atmospherical electricity which take place with terrible explosions, and not seldom with destructive violence, there are others of a more harmless nature, unaccompanied by the rolling of thunder or the flashing of incendiary lightning. Of this kind is the appearance of small flames or jets of fire, which are sometimes seen to issue in stormy weather from prominent objects, such as the masts of ships or the points of lances.

A phenomenon so striking could not fail to attract attention since the remotest times, and we consequently find it playing a part in the mythology of the ancients, and repeatedly mentioned in their historical annals.

Diodorus Siculus relates that the ship Argo,' having been assailed by a tempest during the expedition of Jason to Colchis, Orpheus implored the gods of Samothrace, when two stars placed themselves upon the heads of Castor and Pollux, who took part in the Argonautic voyage, and the danger immediately ceased. Ever since, adds the historian, the sailors, when threatened by a storm, invoke the gods of Samothrace, and when the two stars appear they are attributed to the tutelary presence of Castor and Pollux, the sons of Jupiter and Leda, and hailed as the certain signs of a prosperous voyage. The appearance of a single flame or

star, on the contrary, was supposed to forebode disaster and shipwreck, and attributed to the presence of mischiefmaking Helena, the ill-famed sister of the Dioscuri. Such was the strange fabric of superstition built upon a simple physical phenomenon!

While the fleet of Lysander was on the point of sailing from the port of Lampsacus to attack the fleet of the Athenians, Plutarch tells us that the stars Castor and Pollux appeared one

on each side of the ship of the Lacedemonian admiral, who soon after, by surprising and capturing the Athenian fleet at Aigos Potamoi, destroyed the supremacy of Athens, and made Sparta for a time the leading state of Greece.

The appearance of jets or brushes of flame on the points of lances and javelins was always considered by the ancients as a lucky omen. Thus when Gylippus on his march to Syracuse saw a star resting upon his lance, he was highly

rejoiced at this sign of divine favour. According to Dionysius of Halicarnassus,' the Romans in the year 251 of Rome, when about to fight against the Sabines with inferior numbers, were greatly encouraged by the flames which appeared on the long iron points of the lances they had stuck into the ground.

Hirtius Pansa, in his 'Commentaries on Cæsar's African War,' 2 relates that in a stormy night, during which a great fall of hail took place, the points of the standards of the fifth legion were seen to emit flames, a circumstance which inspired the army with the confidence of victory; and, according to Procopius, a similar phenomenon appeared on the lances of the soldiers of Belisarius, during the war against the Vandals.

We have also read in Valerius Maximus,3 that while the centurion L. Marcius was haranguing the Roman troops, who were greatly dispirited by the death of P. and Cn. Scipio in Spain, a flame was seen on his helmet. This prodigy had a wonderful effect in raising the courage of the soldiers, who soon after gained a great victory over the Carthaginians.

Though in our days Castor and Pollux are no longer invoked by seamen, yet St. Elmo's fire, as the phenomenon is now called, still maintains its ancient ominous significance among the mariners of the Mediterranean; for though religions and customs change, superstitious ideas are transmitted from century to century.

'On Saturday night' (October 1493), writes Don Diego Columbus in his history of his father's voyage, 'it thundered and rained very much. St. Elmo then showed himself in the foremast with seven lighted tapers-that is, the fires were seen which the sailors suppose to be the body of the saint. Immediately many litanies and prayers were sung on board, for seafarers are persuaded that all danger is past as soon as San Elmo shows himself.'

Herrera informs us that the companions of Magellan shared the same superstition. During a great storm,' says

Antiquit. Roman.' v. 46.

2 Bell. Afric. cap. 41.

3 Dictorum Factorumque memorabilium Libri-De Prodigiis.

the historian, St. Elmo showed himself upon the masts, sometimes with one light, at others with two. These phenomena were welcomed with exclamations and tears of joy.'

6

The French admiral Forbin relates in his Memoirs' another remarkable instance of St. Elmo's fire, which came under his observation in 1696 near the Balearic Islands. 'The night suddenly became profoundly dark, with terrible thunder and lightning. Fearing a heavy gale, I ordered the sails to be reefed. We saw upon the ship more than thirty of St. Elmo's fires. One among others at the top of the vane of the mainmast was above a foot and a half high. I sent up a sailor to bring it down. When he was at the top of the mast he called out that the fire made a noise like that caused by the burning of wet powder. I ordered him to take off the vane and to come down, but scarce had he detached it when the fire left the vane and settled on the top of the mast, so that it was impossible to remove it. It remained there some time, and then gradually disappeared.'

The near relationship of the St. Elmo fire and the thunderstorm is plainly revealed in the following instance:In March 1866, one of these mysterious flames appeared in stormy weather on the top of the mainmast of an iron steamer navigating in the Channel. The captain had the curiosity to examine it close by, and found to his surprise that it emitted no appreciable heat. His own body now served as a conductor to the electrical disengagement, and jets of fire were projected from his fingers' ends without causing any shock or commotion. The phenomenon followed all the fluctuations of the storm. Whenever the wind blew more violently, and the rain fell more heavily, the harmless light increased in splendour.

Similar observations were made in the Atlantic on board the packet-boat 'Imperatrice Eugenie' on the night of December 23, 1869. The weather was squally, accompanied with showers of hail, and luminous brushes of a bluish colour a foot and a half high appeared at the points of the conductors on every mast, while the rigging shone with a phosphoric gleam. These lights made their appearance as soon as the squall reached the ship. Extremely brilliant