THE HANGCHOW BORE 243 



istence of the bore as well as its fluctuations probably depends on a 

 nice balance between various factors, and the irregularity in the depth 

 and form of the estuary renders impossible the exact calculation of the 

 form of the rising tide. The heading back of the sea water by the 

 natural current of the river, and the progressive change in shape of a 

 wave advancing into shallow water, may combine to produce a rapid rise 

 of the tides in rivers. " But the explanation of the bore as resulting 

 from these causes is incomplete because it leaves their relative im- 

 portance indeterminate, and serves rather to explain a rapid rise than 

 an absolutely sudden one." " It seems impossible from the mere in- 

 spection of an estuary, to say whether there would be a bore there; 

 we could only say that the situation looked promising or the reverse." 

 " . . . as in many other physical problems, we must rest satisfied 

 with a general comprehension of the causes which produce the observed 

 result." The description we have attempted may serve to give those 

 who have not seen such a wonder some idea of the really marvelous 

 phenomenon, but the best way to become familiar with its character- 

 istics is to go and see it for yourself. 



