THE TEADE. WINDS. 241 



motion the whole mass of the atmosphere. The rivers of the air repro- 

 duce, only in greater proportions, on account of their larger domain, 

 the immense curves of the oceanic currents. The two fluids in move- 

 ment, winds and marine currents, are superposed in their march 

 around the planet. 



In the tropical zone, where the incessant attraction produced by the 

 ascending current determines a constant afflux of masses of air coming 

 from the north and south, the circulatory system of the winds pos- 

 sesses in general a tolerable regularity. In this part of the terrestrial 

 sphere the aerial masses move uniformly, those of the northern hemi- 

 sphere in the direction from north-east to south-west, and those of the 

 southern hemisphere in the direction from south-east to north-west. 

 Thus two atmospheric currents do not cease to flow obliquely to meet 

 each other. These are the " trade-winds," which the ancients hardly 

 knew, and of which the complete discovery was reserved for the great 

 Spanish and Portuguese navigators. Among all the marvels that 

 they discovered in the tropical regions, none astonished them more 

 than these breezes, blowing invariably from the same point of the 

 horizon. Accustomed to the changing and irregular winds of the 

 European seas, the sailors were almost terrified at the constancy 

 of these winds, which carried them towards the equator, and never 

 flowed back again in the direction of their country. The companions 

 of Columbus saw in it the effect of the craft of the devil, and asked 

 with terror if all this movement of the aerial waves was not directed to- 

 wards some gulf, situated at the limits of the world. Nevertheless, navi- 

 gators were soon familiarized with the tranquil latitudes traversed by 

 the trade-winds. The Spanish sailors formerly called the tropical part 

 of the Atlantic Ocean el golf o de las Damas (the ladies' sea) because there 

 one could confide the helm of a ship to a young girl without danger. 

 Indeed, according to Yarenius, the sailors setting out from Acapulco 

 could fall asleep without paying attention to the rudder, with the cer- 

 tainty of being conducted by the wind across the calm waters of the 

 Pacific, to the shores of the Philippines. Struck with the great ad- 

 vantages which the constancy of the trade-winds present to navigation, 

 the English have given them this name. The old term, vents alizes, 

 by which the French sailors designate them, indicates an equal con^ 

 tinuous and regular movement. 



Still, it must be said, these winds have not such a certain march, 

 that we can count on them, as on the return of the heavenly bodies. 

 The alternation of the seasons and the great atmospheric disturbances 

 make them oscillate from rio^ht to left, retard or accelerate them, and 



