H2 POPULAR LECTURES AND ADDRESSES. 



after the first high water, and then the water 

 rises again a very little more for an hour and a 

 half or two hours, before it begins to fall to low 

 water. 



I shall endeavour to refer to this subject again. 

 It is not merely the Isle of Wight that gives rise 

 to the phenomenon. The influence extends to 

 the east as far as Christchurch, and is reversed at 

 Portland, and we have the double or the prolonged 

 high water also over at Havre ; therefore, it is 

 clearly not, as it has been supposed to be, due to 

 the Isle of Wight. 



But now I must come back to the question 

 What are the " Tides " ? Is a " tidal wave " a 

 tide ? What is called in the newspapers a " tidal 

 wave " rises sometimes in a few minutes, does great 

 destruction, and goes down again, somewhat less 

 rapidly. There are frequent instances in all parts 

 of the world of the occurrence of that phenomenon. 

 Such motions of the water, however, are not tides ; 

 they are usually caused by earthquakes. But \ve 

 are apt to call any not very short-time rise and 

 fall of the water a tide, as when standing on the 



