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The Museum Gazette 



the times and character of their tides — four distinct high 

 tides occurring in some places in each day. 



To speak accurately, there are not two tides in every day. 

 A longer period than twenty-four hours is required for the com- 

 pletion of two tides. From one high water to another the 

 exact time is twelve hours and twenty-five minutes, and as this 

 occurs twice daily there must be an interval of fifty minutes 

 between the high water tide of one morning or evening and 

 that of nearly the same time on the following day. 



The two tides occur in each lunar day, but as that day is 

 about fifty minutes longer than the solar or civil day, high tides 

 occur, as has just been said, on each successive civil day about 

 fifty minutes later than the corresponding ones on the previous 

 day. 



The range as to the rise and fall of the tide is estimated at 

 most places on our coasts by the extent of beach which is laid 

 bare at low tide and that covered at high water. In narrow 

 rivers and on coasts where the cliffs are precipitous the measure 

 mostly is simply of depth. When the tides are good the 

 depth may exceed twenty feet, but it varies much at different 

 places. When, under the influence of the moon and sun acting 

 together, the tides are good for several days in succession they 

 are called <£ spring tides," and when the converse happens and 

 they are poor for several days they are called " neap." A neap 

 tide neither comes up far nor goes down far, whilst a spring 

 tide exceeds in both directions. Spring tides and neap tides 

 alternate regularly and both occur twice in the lunar month. 

 The tides are good or " spring" during the days following New 

 and Full moon, and they are "neap" at the middle periods 

 between these events. 



When you get to the seaside consult your almanac and take 

 a slip of paper and record the dates of the full and new 

 moon for the whole of your visit. You will then be able to 

 note down also the times when the tides will be good and 

 when poor, and subsequently to see whether your predictions 

 are fulfilled. 



