1864.] 



293 



[Chase. 



Semi-Mexstrual Inequality at London. 



The recjular recurrence of the aerial tides at stated hours, is a suffi- 

 cient evidence of their dependence upon the relative positions of the 

 earth and sun. Though the differential effect of the moon's attrac- 

 tion is greater than that of the sun's, the intensity of the solar attrac- 

 tion is much the greater. I am inclined to believe that this intensity 

 is manifested in a greater stability of the solar attraction-spheroid, 

 Vfhich prevents its yielding readily to the effects of rotation. 



Lubbock quotes from Williams's Narrative of Missionary Enter- 

 prises, p. 172, his remarks on the " -well-known fact that the tides in 

 Tahiti and the Society Islands are uniform throughout the year, both 

 as to the time of the ebb and flow, and the height of the rise and 

 fall; it being high water invariably at noon and midnight, and low 

 water at six in the morning and evening. The total range from low 

 to high water seldom exceeds eighteen inches or two feet." The 

 earth's rotation, producing an alternate half-day's acceleration and 

 retardation in the eastward motion of the water, should create a ten- 

 dency to tides of this character, and the situation of the islands 

 mentioned, is peculiarly favorable for the development of that ten- 

 dency. Were they near a continent or at the entrance of a gradu- 

 ally narrowing ocean, they would feel the influence of the derivative 

 tide which accumulates the attractive energies of the moon for seve- 

 ral successive transits, and the tides would vary with the moon, as 

 upon our own shores : but the nearly uninterrupted ocean sweep of 

 80° to the eastward may give the combined rotation and solar waves 

 such resistless force, that they can easily overcome the weak intensity 



