Degree

Degree, the 360th part of the circumference of a circle; see CIRCLE, GRADUATION. A degree of latitude is the length along a Meridian (q.v.), such that the difference of latitude between its north and south ends is one degree—i.e. from the two positions the altitude of the same star is seen to differ by one degree (see LATITUDE). Another definition is that two points on the earth's surface differ in latitude by one degree, when the verticals at these points make angles with the plane of the equator, differing by one degree. Were the earth perfectly spherical in shape, this distance along a meridian would be exactly equal to $\backslash frac\{1\}\{360\}$ of the whole meridian, and would be the same at all parts of the earth's surface. But owing to its oblately spheroidal shape it increases from the equator, where the curvature is greater, to the poles, where it is less curved. From geodetical measurements made, it is found that at the equator the length of a degree of latitude is 362746.4 feet; while at the poles it is 366479.8 feet. The differences between the length of the degree of latitude in different latitudes, thus ascertained by actual measurement, is one of the proofs that the figure of the earth is not that of a sphere but that of an oblate ellipsoid.

A degree of longitude is the length between two meridians that make an angle of one degree at the poles, measured by the arc of a circle parallel to the equator passing between them. It is clear that this space is greatest at the equator, and vanishes at the poles; and it can be shown that it varies with the cosine of the angle of latitude. The annexed table shows the lengths of a degree of longitude for places at every degree of latitude from 0° to 90°. It is computed on the supposition that the earth is a sphere.