THE EARTH. IVS 



duce nothing similar by any exiieriments hitherto made, remains 

 for some happier accident to discover. Our progress in the 

 knowledge of nature is slow ; and it is a mortifying considera- 

 tion, that we are hitherto more indebted for success to chance 

 liian industry'. 



CHAP. XVI. 



OF THE TIDES MOTION, AND CURRENTS, OF THE SEA ; 

 WITH THEIR EFFECTS. 



It was said in the former chapter, that the waters of the sea 

 were kept sweet by their motion ; without which they would 

 soon putrefy, and spread universal infection. If we look for 

 final causes, here indeed we have a great and an obvious one 

 that presents itself before us. Had the sea been made without 

 motion, and resembling a pool of stagnant water, the noble races 

 of animated nature would shortly be at an end. Nothing would 

 then be left alive but swarms of ill-formed creatures, 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 concus- 

 sion 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, if security and ease, enjoy a 

 short life, and putrefying, thus again give nourishment 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 pro- 

 duce 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 the south towards the north ; in 



which motion or flux, which lasts about six hours, the soa gra- 



^ ii 



