158 LIGHT SCIENCE FOR LEISURE HOURS. 



drain which the solar wave exerts upon it at the time 

 of neap tides. Nor would the large lunar tidal wave 

 produce an exceptionally high tide, even though it 

 were not the time of "neap," or were tolerably near 

 the time of " spring " tides. Only when it happens 

 that a large lunar wave combines fully with the solar 

 wave do we get very high tides. And when, in ad- 

 dition to this relation, we have the solar wave nearly 

 at a maximum, we get the highest of all possible tides. 

 This is what will happen, or all but happen, on Octobor 

 5th next. The combination of circumstances is almost 

 the most effective that can possibly exist. 



But, after all, high tides depend very importantly 

 on other considerations than astronomical ones. Most 

 of us remember how a predicted high tide some two 

 years ago turned out to be very moderate, or, if we 

 may use the expression, a very "one-horse" aifair 

 indeed, because the winds had not been consulted, and 

 exerted their influence against the astronomers. A 

 long succession of winds blowing off-shore would re- 

 duce a spring tide to a height scarcely exceeding the 

 ordinary neap. On the other hand, if we should have 

 a long succession of westerly winds from the Atlantic 

 before the approaching high tide, it is certain that a 

 large amount of mischief may be done in some of our 

 river-side regions.* 



As for the predicted weather changes, they may bo 

 * The wave did little mischief. 



