Lesson xxxi.] TIDES. 



Tide is continually diminished, til! at last it en- 

 tirely vanishes, and leaves only one Tide in the day. 

 Hence it is found by observation, that, when the 

 moon has declination, there is only one Tide in 

 twenty-four hours in all places in the polar regions, 

 in which the moon is either always above or al- 

 ways below the horizon, during a whole rotation 

 of the earth about its axis. 



These things would happen uniformly in the 

 manner above described, if the whole surface of the 

 earth were covered with water ; but since there is a 

 multitude of islands, continents, &c. which inter- 

 rupt the natural course of the water, varieties of 

 appearances are to be met with in different places, 

 which cannot be explained without regarding the 

 situation of shores, straits, and other objects : 

 and as this would lead me too great a length, with- 

 out oeing of much utility, I shall here take my 

 leave of the subject, with remarking, that the most 

 correct popular view of it with which I am ac- 

 quainted is given by Laplace in his Exposition du 

 Systems du Monde. 



LESSON 



