On the connexion of the physical sciences / By Mrs. Somerville.

  • Mary Somerville
Date:
1834
Catalogue details

Licence: Public Domain Mark

Credit: On the connexion of the physical sciences / By Mrs. Somerville. Source: Wellcome Collection.

    53/478 page 41
    observations, jierfcctly confirms these; results of analysis. Future ages will develop these great inequalities, which at some most distant period will amount to many circumferences. They are indeed periodic; hut who shall tell their period ? Millions of years must elapse before that great cycle is accomplished ; but ‘ such changes, though rare in time, arc frequent in eternity.’ The moon is so near, that the excess of matter at the earth’s equator occasions periodic variations in her longitude, and also that remarkable inequa- lity in her latitude already mentioned as a nuta- tion in the lunar orbit, which diminishes its inclination to the ecliptic when the moon’s ascend- ing node coincides with the equinox of spring, and augments it when that node coincides with the equinox of autumn. As the cause must be proportional to the effect, a comparison of these inequalities, computed from theory, with the same given by observation, shows that the compression of the terrestrial spheroid, or the ratio of the differ- ence between the polar and equatorial diameters, to the diameter of the equator, is Trf,Tl. It is proved analytically that, if a fluid mass of homo- geneous matter, whose particles attract each other inversely as the square of the distance, were to revolve about an axis as the earth does, it would assume the form of a spheroid whose compression
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