The form of our globe, which is that of an oblate spheroid with an ellipticity of about 1⁄299.
The specific mark of this family is the flattening or ellipticity.
Its two diameters are to one another as 17 is to 16; the ellipticity of its disk is manifest to simple inspection.
The extensive sets of observations of gravity provided the basis of calculations of the ellipticity of the earth.
When these were submitted to calculation, each led to the same value of the ellipticity.
This fraction is denominated the ellipticity of the earth,—being the excess of the equatorial over the polar diameter.
The specific difference in the new family, denoted in the general sketch by b, is this ellipticity of the equator.
Their ovalness or "ellipticity" is, however, in each case not by any means of the same degree.
To put it paradoxically, it is an ellipse which has no ellipticity, an oval without any ovalness!
The orbits of Mercury and Mars have an appearance of ellipticity because the sun does not occupy the central point in the diagram.