THE TRADE WIND. 131 



(52.) From these observations it appears that the N.E. Trade undergoes, 

 in the two epochs, considerable change of strength, viz., equal to 0*7 mile 

 in favour of the February and March period ; on the other hand, the S.E. 

 Trade is stronger by 0*4 mile in the August and September period than 

 during that for February and March. 



Comparing the two Trades (N.E. and S.E.) together, it would seem that 

 the S.E. is 1-2 mile stronger than the N.E. 



Again, ships bound to the Southward may generally expect to find the 

 N.E. Trade stronger on the Central route, during February and March, 

 than more to the Eastward ; while in the August and September epoch, 

 they will find this wind blowing with its greatest intensity between the 

 meridians of 20° and 25° W. 



This last observation deserves consideration, because it is generally 

 believed that the wind is stronger in proportion as the distance from the 

 African shore is increased, 



(53.) The N.E. (Hke the S.E.) Trade Wind, blows over a wider area in 

 the Eastern part of the Atlantic than on the American side, as at the 

 meridian of 10° W. they extend from 35° or 38° N. to 25° or 28° S. ; while 

 on the American side the hmits are from 28° or 30° N. to 23° or 25° S. ; 

 but on the Eastern side the intervening space of Calms is much wider. The 

 extent and limits will be best comprehended by an inspection of the diagram 

 of the Winds ; the Umits there shown are taken from the tabular state- 

 ments by Commander Maury and by the Dutch Meteorological Institute, 

 and for the Equatorial region by Captain Toynbee. This will explain the 

 various lines and fluctuations better than a long series of words. 



The Northern Limit of the N.E. Trade Wind, as will be seen, extends 

 on the Eastern side of the Atlantic, that is off the coast of Africa, to lat. 35° 

 as a mean, in August and September, being then at its greatest Northern 

 extent; but it is frequently encountered when in lat. 38°, or sometimes 

 even at 40°. To the Westward of the meridian of 30° the Northern edge 

 seldom extends Northward of 33° or 34°, while toward the Bahamas the 

 Northern hmit is 30° N. This extreme Northern declination appears to 

 be attained in August and September, as stated before, and then following 

 the sun in its southward course, it reaches its Southern limits in March 

 or April. In January, its mean limit on the Eastern side is about the 

 Canaries; over the Eastern half of the Atlantic in about 25° N. ; in the 

 centre about 22° N. ; and over the Bahamas it seldom vibrates to any great 

 extent throughout the year. 



The extent of variation between the Northern edge of the Trade Winds 

 when first encountered, as shown by Maury's Trade Wind Charts, seems 



to be as much as 10 degrees of latitude — a wide range of probabihty and 



in many cases there appears from these charts to be as much chance of 

 meeting them in one latitude as another. Of course this is takin^r into 

 account the Belt of Calms and Variable Winds usually (but not always) 

 found on the edge of the Trades, which will be spoken of presently. 



(54.) The Southern Edge of the N.E. Trade Wind is hmited in the 

 Eastern part by that broad region so embarrassing to the sailor, known as 

 the " Doldrums," or, especially during the Northern summer months, by 

 a set of winds blowing towards the coast of Africa, known of old as the 



