WINDS AND CALMS ON THE TROPIC. 169 



From the lower part of this zone pass out two currents of air, one to feed 

 the N.E. Trades, as before described, and the other to form the Anti-Trades 

 or Passage Winds : and it is fed by the Polar and Tropical counter-currents 

 which flow over these different wind systems. 



(98.) The mean latitude of this belt is from SO'' to 35'^ N., but varying 

 with the motion of the sun in the ecliptic, as explained in (53), page 131. 

 In fact, the Northern edge of the Trade Wind may be taken as the axis 

 over which this belt moves, sometimes of great breadth, as 10° ; at others, 

 not felt at all. The mean position of these Tropical Calms, &c., will be 

 best comprehended from the diagram of the Winds. As is well known, 

 this belt is the line upon which the dreaded Cyclones turn ; they pass to 

 the W.N.W., to the South of it; and to the E.N.E., to the North of it ; 

 showing the origin of the struggle between the Polar and Tropical currents, 

 which is evident in their tremendous phenomena. 



(99.) As was said in (53), page 131, the range over which the Northern 

 limits of the N.E. Trade is met with, seems to be, from Maury's chart, 

 about 10° ; but as this and later meteorological charts cannot be pronounced 

 absolutely perfect, being derived from insufficient data, it may be said that 

 the mean position of the Tropical Calms in the various seasons of the year 

 cannot with certainty be predicted ; but as it does not offer the same obsta- 

 cles to navigation as those of the Equatorial regions, it is of less import- 

 ance to the sailor, who, by ordinary sagacity and prudence, may guard 

 against the squalls, thunder-storms, and calms, which characterize it. 



(100.) To the Westward of the meridian 50" W., — that is, the Western 

 half of the N.E. Trade in the North Atlantic — the Trades are very light 

 during the months of September and October ; perhaps at other times of 

 the summer and autumn. They will be most felt between the parallels of 

 15° and 25° ; but not with any certainty near the American coast. This 

 region may therefore be added to the Tropical Calms during these months. 



As examples of the winds, as observed upon the lands lying in this belt, 

 we select the remarks upon the Bermudas. 



(101.) Bermuda. — The winter, or cold season, at Bermuda, is the most 

 agreeable, and lasts from November to March, the mean temperature being 

 60° ; the predominant winds are then from the Westward ; if to the North- 

 ward of this, fine, hard weather, with a clear sky, accompanies them. This 

 is the favourable time for refitting ship, painting, &c. The close of this is 

 often a very fine, bright day, with little wind and partial calms, when the 

 wind is certain of going round to the S. W. ; the weather becoming hazy, 

 damp, subject to heavy rains and gales. The thermometer immediately 

 attains 60^ to 70°. These alternate North- Westerly and South- Westerly 

 winds prevail through nine months of the year, the wind remaining at no 

 other point for any length of time. This change is exhibited by a difference 

 of 14° in the temperature. At this season it seems advisable for ships 

 bound to the southward to wait and take the first set-in of the North- 

 westerly winds. In most cases, it will ensure a quick run to the Variables, 

 and often to the Trades. — Mr. H. Davy. 



In the latter part of February, spring commences, and the weather usually 

 continues mild, \^ith refreshing showers of rain and gentle breezes from the 



N. A. 0. 23 



