HUEEICANES. 261 



Square 3 (see Sections on Trade Winds and Passages), he found that at 

 the Northern verge of the S.E. Trade the upper clouds very frequently 

 moved from N.E., and Squalls would come from N.E., though the steady 

 lower wind was always S.E. or Southerly, as if the upper current of air 

 sometimes forced its way downward through the lower current, causing 

 the Squall, and then rose again. <« 



White Squall. — On November 14th, 1878, when 160 miles off Cape Sable, 

 the barque Bel Stuart was struck by a White Squall, in a comparatively 

 smooth sea and clear sky. At 6 p.m., all hands being on deck, a strange 

 sighing of the wind was noticed, and the sky became suddenly threaten- 

 ing, though the barometer showed a rising tendency. Without a moment's 

 notice, the sea forward seemed to swell up to meet the lowering sky, and 

 swept across the bows, doing much damage to the masts and spars. In a 

 moment the barque was left a comparative wreck wallowing in the trough 

 of the tremendous seas. This seems to show that the vessel ran into an 

 incipient Tornado and Waterspout. 



(207.) Tornados are formed in a similar manner to Cyclones, from which 

 they differ chiefly in size. Both have a gyratory and forward motion, but 

 a Tornado is much less in area, very rarely attaining a diameter of 1 mile. 

 It consists of an ascending column of air rotating around a region of very 

 low pressure, sometimes the direction and rotation being with watch- 

 hands, but mostly the reverse, according to the researches of Mr. Finley 

 on 600 Tornados occurring in the United States. When these Tornados 

 pass over the land, the central pressure is so low, that the air contained 

 in closed dwellings has been known to burst the doors and windows out- 

 ward, while the enormous velocity of the wind itself sweeps everything 

 before it. 



The Tornado derives its appellation from the Portuguese, signifying a 

 whirlwind. It is known on all the coast of Africa, between the Eio Nurez, 

 in lat. 10^° N., and the Equator, but is most severely felt on the Windward 

 Coast, and seems intended by Divine Providence to expel the noxious 

 matter with which the air is so frequently charged. The Tornado first 

 announces itself by the appearance of a small silvery cloud in the zenith, 

 which gradually increases and descends towards the horizon, and the scene 

 becomes veiled over with the most impenetrable darkness. At this moment 

 the functions of nature seem to be paralyzed, and the elements to have 

 ceased their operations ; the most profound and solemn stillness reigns 

 around, with scarcely a breath of air from the heavens, in consequence of 

 which the whole physical system feels oppressed with sensations of 

 approaching suffocation ; violent and reverberated peals of distant thunder 

 and lightning commence, gradually advancing and increasing to an extreme 

 not easy to describe ; the atmosphere, at times, in a continued blaze for 

 minutes, without intermission. At length the gust arrives with sometimes 

 the greatest irresistible violence, the impulse of which no sails can fre- 

 quently withstand. It is fortunately not of long duration, extending from 

 one to three hours, and concludes with a furious deluge of rain, which 

 descends rather in columns than in drops. The great danger is in the 

 sudden impulse of the gust, which would immediately dismast or overturn 

 a vessel unprepared for the event. Nothing can be more exquisitely de- 



