The Tides. 221 



of 7-8 feet, and, the main wave having reached Spithead, another 

 tide enters here a little over one hour later with a range of 12 to 

 13 feet so that there is a second high water 2 J hours after the first 

 at Southampton; the second tide passes also to the west from 

 "Cowes," after the first has passed making a second highwater at 

 Lymington. The two parts of the tide wave remain distinct. 

 The point of meeting or crossing at Cowes is such as to leave the 

 general direction of the tides at rightangles and it can be prac- 

 tically demonstrated that two sets of waves may travel in this 

 manner without any serious interference. 



"When, however, two tides .aeet in the ocean, they will form one 

 w.nve which will progress in a direction which will be the resultant 

 of the previous direction and velocity of the separate tides. We 

 must also bear in mind that in ail^ excepting rare cases, the tide 

 in questiou supplants a wave whicii occupied the same location 

 twelve hours before. 



The semi-diurnal tides may differ to such an extent that the 

 high water of one corresponds with the low water of the other, 

 and may leave the impression of but one or a diurnal tide, the 

 appellation however is a misnomer, there being really no diurnal 

 tide ; the distortion can be recognized in every case so that there 

 is no question of there being two tides. This compounding is not 

 due to a meeting of tides but to the location and time of the orig- 

 inating impulse as we will see further on. 



It happens at times that one of the semi-diurnal tides is entirely 

 lost and this is, when the wave is small and travels free by its 

 own vis viva after the force is removed, being constantly retarded 

 in its movement and at length unable any longer to overcome the 

 resistance of friction the wave finally stops and is lost. This is 

 the case in the gulf tides when the moon's declination is maxi- 

 mum, one of the waves is so small that it is scarcely distinguisha- 

 ble and is at times lost before reaching the coast. 



Where two tides of the same type but of nifferent origin meet 

 as at Cape Horn and the Cape of Good Ilope, they unite and 

 become one wave. The meeting of the tide off the capes will 

 account for the turbulent condition of the sea in these localities. 



Only a few of many tidal theories are noticed tn the foregoing 



