The most direct and perfect application of mathematical and astronomical
science to the delineation of the surface of the globe, so as to ascertain
its exact form, and the exact extent of degrees of latitude in different
parts of it, has been made by the English and French; and much to their
honour, by them in conjunction. The first modern measurement of degrees of
latitude was made by an Englishman of the name of Norwood: he ascertained
the difference of latitude between London and York in 1635, and then
measured their distance: from these premises he calculated, that the length
of a degree was 122,399 English yards. At this time there was no reason to
suppose that the earth was flattened at the Poles. Shortly afterwards, it
having been discovered that the weights of bodies were less at the equator
than at Paris, Huygens and Cassini directed their attention, as we have
already stated, to the subject of the figure of the earth. In 1670 Picard
measured an arc of the meridian in France; and in 1718, the whole area
extending through France was measured by Cassini and other philosophers.
The results of this measurement seemed to disprove Newton's theory, that
the curvature of the earth diminished as we recede from the equator. To
remove all doubts, an arc near the equator was measured in Peru, by some
French and Spanish astronomers; and an arc near the arctic circle by some
French and Swedish astronomers; the result was a confirmation of Newton's
theory, and that the equatorial diameter exceeded the polar by about 1/204
part of the whole.
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