SUN, MOON, AND TIDES — COLBERT 



193 



a minor tide-producing force and there is a small daily rise and fall. 

 A tidal basin exists in the extreme western part of the Indian Ocean. 

 Its geographical limits are well defined on one side and end by the 

 east coast of Africa and the shore line of the Arabian Sea. The 

 island of Madagascar lies along the middle of the other side. This 

 basin is overlapped by two other basins which extend across the 

 Indian Ocean from east to west (fig. 4). The southern of these is 

 clearly defined at the ends by the coasts of Africa and Australia. 

 The northern basin is bounded mainly by the south coast of the con- 

 tinent of Asia and the shore line of northwest Australia. 



Figure 4. — Tidal basins in the Indian Ocean. 



Where the east-west basins overlap the north-south basin in the 

 western part of the Indian Ocean, high water comes halfway 

 through the period of oscillation of the overlapping basins, one oc- 

 curring at the third hour and the other at the sixth hour. The sta- 

 tionary wave of one basin will bring high water at the time when the 

 water in the other has receded to sea level and neither the time nor 

 range of the tide is influenced by the overlap. 



High water occurs at the third hour along the shore line of the 

 northern part of the Bay of Bengal, in sections of the coast of Aus- 



