CuAr. XJll] THE TIDES. 155 



the surface of the earth, appears to be indicated in 

 the North Atlantic Ocean by the great height of the 

 tides in the temperate zones compared with the rise 

 and fall in the equatorial regions. For the water 

 moved eastwards in the temperate zones is a counter- 

 poise to that moved westwards in the equatorial 

 regions by the same tide : and since the space from 

 Nova Scotia to France and the British Isles, in which 

 the eastward tide moves, is very narrow compared 

 to that extending through the equatorial regions from 

 the Gulf of Guinea to the Gulf of Mexico — therefore, 

 since the tide in the east of the temperate zone must 

 counterbalance that in the west of the equatorial 

 regions, its rise and fall must be greater in propor- 

 tion with the lesser extent of ocean through which it 

 moves. So also with the tides in the west of the 

 temperate zone, which counterbalance those in the 

 east of the equatorial zone ; the rise and fall about 

 Nova Scotia is far greater than that in the Gulf of 

 Guinea, for the same reason that the rise and fall 

 about the British Isles is greater than that about the 

 West Indies. This counterbalancing movement of 

 the tides is still more strikingly indicated by the 

 contrast between the rise and fall in the temperate 

 zone of the North Atlantic Ocean, compared with 

 that in the temperate zone of the southern hemi- 

 sphere. In the latter case the tide, which moves 

 eastwards, has a more or less clear sweep from about 

 the Falkland Islands and the River Plate to the 



