The comparison
of eleven measurements of degrees (in which are included three
extra-European, namely, the old Peruvian and two East Indian) gives,
according to the most strictly theoretical requirements allowed for by
Bessel,* a compression
p 166
of 1/299th.
[footnote] *According to Bessel's examination of ten measurements of
degrees, in which the error discovered by Poissant in the calculation of the
French measurements is taken into consideration (Schumacher, 'Astron.
Nachr.', 1841, No. 438, s. 116), the semi-axis major of the elliptical
spheroid of revolution to which the irregular figure of the Earth most
closely approximates is 3,272,077.14 toises, or 20,924,774 feet; the
semi-axis minor, 3,261,159,83 toises, or 20,854,821 feet; and the amount of
compression or eccentricity 1/299.152d; the length of a mean degree of the
meridian, 57,013.109 toises, or 364,596 feet, with an error of + 2.8403
toises, or 18.16 feet, whence the length of a geographical mile is 3807.23
toises, or 6086.7 feet. Previous combinations of measurements of degrees
varied between 1/302d and 1/297th; thus Walbeck ('De Forma of Magnitudine
telluris in demensis arcubus Meridiani definiendis', 1819) gives 1/30278th:
Ed. Schmidt ('Lehrbuch der Mathem.
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