THE EARTH, 



then be left alive but swarms of ill-formed crea- 

 tures, with scarcely more than vegetable life ; and 

 subsisting by putrefaction. Were this extensive 

 bed of waters entirely quiescent, millions of the 

 smaller reptile kinds would there find a proper 

 retreat to breed and multiply in ; they would find 

 there no agitation, no concussion in the parts of 

 the fluid to crush their feeble frames, or to force 

 them from the places where they were bred; there 

 they would multiply in security and ease, enjoy 

 a short life, and putrefying, thus again give nou- 

 rishment to numberless others, as little worthy of 

 existence as themselves. But the motion of this 

 great element effectually destroys the number of 

 these viler creatures; its currents and its tides 

 produce continual agitations, the shock of which 

 they are not able to endure ; the parts of the fluid 

 rubbing against each other, destroy all viscidities ; 

 and the ocean, if I may so express it, acquires 

 health by exercise. 



The most obvious motion of the sea, and the 

 most generally acknowledged, is that of its tides. 

 This element is observed to flow for certain hours, 

 from south towards the north ; in which mo- 

 tion or flux, which lasts about six hours, the sea 

 gradually swells ; -so that entering the mouths of 

 rivers, it drives back the river waters to their 

 heads. After a continual flux of six hours, the sea 

 seems to rest for a quarter of an hour ; and then 

 begins to ebb, or retire back again, from north to 

 south, for six hours more ; in which time the 

 waters sinking, the rivers resume their natural 

 course. After a seeming pause of a quarter of an 



