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The elucidation of the theory of centripetal and disturbing forces is necessarily less complete. Still... a general conception of the nature of the action of those forces... sufficient to preserve the student from the gross errors... may be obtained from explanations like those here offered. The methods of ascertaining the weight of the Earth and other bodies are... more difficult of explanation; yet... something may be done even in these.
— GEORGE BIDDELL AIRY