^^ 



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120 



TIDES. 



[Sect. IV. 



high water, except at the head of a bay or creek, 

 am of flood commonly runs for some time 



from 



The 



often for hoiirs 



after the time of high water. 



In the 



way, the stream of ebb rmis for some time after 1 



same 



CSV 



:r^. i- 



water. 



33. The time at which the stream turns is often dif- 

 ferent at different distances from the shore ; but the time 

 of high water is not different at these points. In general, 

 what is wanted in tide observations is the time of hicfh 

 water, not the time of slack imter. 



With regard to the streams of flow and ebb, they are 

 often not merely two streams in opposite directions at 

 different times of the tide ; they generally turn succes- 

 sively into several directions, so as to go quite round the 

 compass in one complete tide; either in the direction 

 N. E, S. W. (with the sun), or N. W. S. E. (against the 

 sun). It is desirable to note which of these ways the tide- 

 stream goes round, as this fact may help to determine 

 which side the tide- wave comes from. 



One 



tide observatioi 





one place to another. 

 This 



is to trace the progress of the tide from 



i may be done in some measure by determining the 

 estaUishments of a series of places in the region which 

 we have to consider. For these establishments, reduced 

 to Greenwich time by allowing for the longitude, give the 

 time at which the tide is at each place, and hence its 



progress. 



35. The progress of the tide may be conceived as the 



progress ot a verv wide wa 

 to each place in succession. 



8 





Sect 



IV 1 



Ijut* 



the 



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motion < 



of the 

 hen th 

 'hen th 



w 



36. 1 



determii 

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age 



Art. 1 7 £ 



37. In 



usmg 



the 



better to i 



all the liii 



For the 



the tide {i 

 Th 



e me 



40m, less i 

 age of the 

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