S3 NATURAL HISTORY. 



this pait of the sea is first elevated ; the surface of 

 the adjacent parts is also elevated, but not so much ; 

 and the waters at the bottom of all these parts are 

 raised by the same cause. Thus as the whole portion 

 of water under the moon is raised, the waters at a 

 distance, upon which no attraction is exerted, must 

 necessarily rush forward with precipitation to supply 

 the place of those which were drawn towards the 

 moon. It is in this manner that the high tide is pro-* 

 duced, which is more or less perceivable in different 

 coasts, and which agitates the sea not only at the 

 surface, but at the greatest depths. The ebb is a 

 consequence of the natural disposition of the water, 

 which when no lon'ger acted upon by the moon, sub- 

 sides, and returns to occupy those shores from which 

 it had been forced to retire by an external cause. 



Nothing is more irregular in our climates than the 

 fiourse of the winds ; but there are countries where 

 this irregularity does not exist, and others where the 

 wind blows constantly in the same direction. 



There are several causes which influence the mo- 

 tions of the air, but the most powerful is the heat of 

 the sun, which by rarifying the air produces an influx 

 of the cold air, which is a heavier fluid, and con- 

 sequently presses in upon that which is rarified and 

 light, and produces a stream or current air. In the 

 torrid zone this effect is more uniformly manifest than 

 in other parts of the world. In the regions near the 

 equinoctial line a continual rarefaction is produced by 

 the sun, and a constant current of air follows that lu- 

 minary from east to west. This easterly wind blows 

 so generally in the Pacific Ocean, that the ships 

 which sail from Acapulca to the Philippines, perform 

 a voyage of 2700 leagues in less than two month?. 



