LESSON XVII, 



ON WINDS. 



Trade-winds, observing well their stated course,' 

 To human good employ their powerful force : 

 The loaded ships across the ocean fann'd 

 By steady galen, spread commerce through the land. 

 These you observe but have you no desire 

 The hidden Spring of such effects t'inqnire? 

 Or, when contending winds around you blow, 

 Do you ne'er wish the cause of them to know ? 



XlITHERTO our reflections have carried us no 

 farther than to consider the air in a motionless 

 state ; but as this fluid mass is frequently in motion, 

 and that too sometimes in a violent degree, it 

 would be almost unpardonable to pass by such an 

 obvious effect without paying some attention to it, 

 Air in a current-like motion is known by the 

 nam of wind. Though the winds in a temperate 

 zone of the earth are very inconstant and change- 

 able, yet this is not the case in every part of the 

 terrestrial globe j for in the torrid zone and some 

 other parts, the winds are generally very uniform 

 and constant in their directions, as will appear 

 from the following facts relative to them : 



1. Over the Atlantic and Pacific oceans, parli- 



' ~ 



cularly between thirty degrees of North and thirty 

 degrees of South latitude, the Trade-winds, as they 



are 



