APPENDIX. 289 



4. The momentum acquired by a body of water in thus sinking 

 back to the position it should occupy, with reference to the earth's 

 attraction only, carries it beyond that position to one from which it 

 has a tendency to recoil again — and so to keep up an oscillation 

 until brought to rest by the friction of its bed. (Attraction of the 

 moon and sun not considered.) 



5. The recurring influences of the moon and sun are checks on 

 these oscillations, and prevent their taking place more than once 

 between each separate raising of the water in consequence of their 

 attractions. 



6. Different zones (or widths measured by latitude) of an ocean, 

 may move differently, each having waves and oscillations at times 

 differing from those of an adjoining zone, in consequence of one 

 having more or less longitude, depth, or freedom from obstacles than 

 another. 



7. Original waves and oscillations combine with, and modify one 

 another, according to their relative magnitude, momentum, and 

 direction. 



8. The natural tendency of tide-waves, and oceanic librations, is 

 from east to west ; and of oscillations, from west to east, and east 

 to west also : but derivative waves or oscillations move in various 

 directions according to primary impulse, and local configuration of 

 the bed of rn ocean. 



Conformably to these conclusions, I will now try to explain a few 

 of the more remarkable anomalies of tides, in various parts of the 

 world : taking it for granted that the reader is acquainted vfith 

 existing works on the subject, especially those of Mr. Whewell,* 

 and the brief but comprehensive and explanatory view taken by Sir 

 J. Herschel in his treatise on astronomy. •}■ 



I mentioned that between Callao and the western shores of the 

 Pacific, in the parallel of about 12° south, no comparison of times 

 can be trusted ? Why not ? may be asked. Four or five hours west 

 of Callao, there is a multitude of islands which checks the libratiou of 

 the ocean. Another tide wave forms westward of them, on a small 

 scale, and it is by this second tide, altered by derivative tides 



* Published in the Philosophical Transactions. 



+ Cabinet Cyclopaedia. A Treatise on Astronomy, chap, xi., pp. 334, 

 5, 6, 7, 8, 9. 



