ELEVATION OF TIDES. 



of a very high or spring-tide, as in Jig. 2, where the 

 tide at a and b has risen extremely high, while at 

 c and d it has fallen correspondingly low. When 



Fig. 2. 



they act in opposition to each other, as at the moon's 

 quarter, there occurs a very low or neap-tide. In 

 fig. 3 the moon has raised high tide at a and 6, but 

 the sun has counteracted its influence to some ex- 

 tent at c and d, thus producing neap-tides, which 



Fig. S. 



neither rise so high nor fall so low 

 as do other tides. Tides attain vari- 

 ous elevations in different parts of 

 the world, partly owing to local influ- 

 ences. In the Bristol Channel the 

 tide rises to nearly sixty feet, while in the Medi- 

 terranean it is extremely small, owing to the land- 

 locked nature of that sea preventing the tidal 

 wave from having its full effect. Up some gulfs 

 and estuaries the tides sweep with the violence of a 



