The discussion in the several versions of The Earth by Jeffreys (third edition, 1952, for example)  relative to the ellipticity of the Earth does not demonstrate, as generally believed, that the Earth has the shape of a rotating liquid. His development in conjunction with the work of H. Lamb (1945)  shows unequivocally that the Earth is much less oblate than required if it were behaving as a liquid mass. It is not true that the observations of Bouguer in the late 1700's regarding the actual ellipticity of the Earth demonstrated the liquidity of the Earth with mass concentrated towards the center. In fact, proper interpretation of his data would have shown that the Earth's ellipticity results from its great strength, not its weakness. Data available today establish that great strength resides in the lower mantle and has in all probability resided there from the time of the Earth's origin. This strength results in the need for reinterpretation of Earth behavior and operative processes.
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What ??a = 1/298 and C/Ma2 = 0.333 really tell us about the Earth