ced the figure to 18,000
miles, or about one seventh too small. The circumference in the latitude
of Gibraltar he estimated at 14,000 miles; the length of the Oecumene,
or Inhabited World, he called 7,000; the distance across the Atlantic
from the Spanish strand to the eastern shores of Asia was the other
7,000. The error of Posidonius was partially rectified by Ptolemy, who
made the equatorial circumference 20,400 geographical miles, and the
length of a degree 56.6 miles.[459] This estimate, in which the error
was less than one sixteenth, prevailed until modern times. Ptolemy also
supposed the Inhabited World to extend over about half the circumference
of the temperate zone, but the other half he imagined as consisting
largely of bad lands, quagmires, and land-locked seas, instead of a vast
and open ocean.[460]

[Footnote 458: See Herschel's _Outlines of Astronomy_, p. 140.
For an account of the method employed by Eratosthenes, see
Delambre, _Histoire de l'astronomie ancienne_, tom. i. pp.
86-91; Lewis, _Astronomy of the Ancients_, p. 198.]

[Footnote 459: See Bunbury's _History of Ancient Geography_,
vol. ii. pp. 95-97, 546-579; Mueller and Donaldson, _History of
Greek Literature_, vol. iii. p. 268.]

[Footnote 460: Strabo, in arguing against this theory of bad
lands, etc., as obstacles to ocean navigation--a theory which
seems to be at least as old as Hipparchus--has a passage which
finely expresses the loneliness of the sea:--[Greek: Hoite gar
periplein epicheiresantes, eita anastrepsantes, ouch hypo
epeirou tinos antipiptouses kai kolyouses, ton epekeina ploun
anakrousthenai phasin, alla hypo aporias kai eremias, ouden
hetton tes thalattes echouses ton poron] (lib. i. cap. i. Sec. 8).
When one thinks of this [Greek: aporia] and [Greek: eremia],
one fancies oneself far out on the Atlantic, alone in an open
boat on a cloudy night, bewildered and hopeless.]

[Sidenote: Toscanelli's calculation of the size of the earth,]

[Sidenote: and of the position of Cipango.]

Ptolemy's opinion as to the length of the Inhabited World was
considerably modified in the minds of those writers who toward the end
of the Middle Ages had been strongly impressed by the book of Marco
Polo. Among these persons was Toscanelli. This excellent astronomer
calculated the earth's e