200 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1952 



greater mass of the sun and that the waters in great tidal basins of 

 the oceans oscillate predominantly to the lunar semidaily tide-produc- 

 ing force. The axis of a tidal basin may be so situated that the waters 

 will receive the maximum effect of one force and the minimum effect 

 of the other. 



In two ocean areas it has been found that the waters are under the 

 minimum influence of the moon. These waters respond to the period of 

 the tide-producing force of the sun. This condition gives rise to the 

 solar tides, which are found at Tahiti and in Torres Strait. Although 

 there is a slight variation, in minutes only, we have at Tahiti the 

 unusual feature of high water coming each day at noon and at mid- 

 night, and low water at 6 in the morning and 6 in the evening. 



The tide at Tahiti has a small range. More recently a larger solar 

 tide has come to light on Tuesday Island, a small island in Torres 

 Strait about 15 miles from the northern point of the Australian main- 

 land. Here the tide has a mean range of over 3 feet, and high water 

 comes about the same time day after day. Low water occurs 6 hours 

 later, also at the same time each day. 



To summarize briefly, we have noted that the tide-producing forces 

 of the sun and the moon bring about the rise and fall of the sea waters 

 of the earth ; and that the response of the waters in the various ocean 

 basins, modified by the hydrographic features and their geographic 

 locations in those basins, results in the varieties of the tide that we 

 observe along the coasts and in the bays, harbors, and seaports of the 

 world. 



