374 



HYDROGRAPHY. 



right angles to the Equator, and afterwards falls calm. Now, it can- 

 not but be perceived that this is almost in opposition to the theory; 

 for if the wind had derived its direction from the rotation of the earth, 

 and its current towards the Equator, its curve would have been dif- 

 ferent, and the current of air would be unable to change its direction, 

 having the same vis inertia as other matter. From this it is to be 

 inferred, that the Trade Winds cannot be caused by the rotation of the 

 earth, combined with surface currents of air flowing from the Poles to 

 the Equatorial regions. Moreover, it would be the reverse of the 

 direction which they now take, and we now know that the currents 

 of air have not sufficient force nor the direction to combine, with the 

 rotary motion of the earth, to produce or maintain a diagonal course 

 of any current of air, much less one as great as the Trade Winds. 



Let us now examine the extent or prevalence of the limits of the 

 Trade Winds. The Northeast Trade Wind of the Atlantic is com- 

 prised within the space between the 9th and 28th degrees north lati- 

 tude on the east, and the 12th and 25th parallel on the w T est, and 

 between the meridian of 18° and 90° west longitude. Its northern 

 edge passes westward, cutting the Tropics at 75° west, and thence 

 along that parallel to 90°, where it ceases. Its southern edge, from 

 the parallel of 9° north latitude, and 30° west longitude, tends 

 towards the parallel of 12° in the longitude of 60° west ; then 

 passes along the coast of Guiana in a west-northwest direction 

 through the Windward Islands, till it reaches the peninsula of 

 Yucatan, in 87° west longitude ; thence it passes into the Gulf of 

 Mexico, and is lost. 



The most eastern point of the Northeast Trade Wind of the Pacific 

 Ocean is found on the meridian of 109° west longitude, and in 4° 

 north latitude. From there it extends in a northwest direction to 

 the longitude of 120° west on the parallel of 26° north latitude. Its 

 northern boundary runs nearly on this parallel to the west until it 

 reaches the meridian of 145° east, to the northward of the Ladrone 

 Islands, where it is merged in or intercepted by the Northeast and 

 Southwest Monsoons, prevailing in the Western Pacific. Its south- 

 western point is in 10° 30' north on the same meridian. The width 

 on its western end is 360 miles less than on its eastern. Its southern 

 edge or boundary makes a slight curve between its eastern and 

 western limits. 



The Southeast Trade Wind of the South Atlantic has its southern 



