T II E

MEASURE

OF T H E >

FnjJ

ARTICLE I.

T HE attempt to determine the Magnitude of theEarth is not new. Many ancient Authors have madethemselves famous by this enquiry. But the most me-morable Attempt for this purpose was that of the Ara-bians, thus Recorded by their Geographer. A greatCircle on the Earth is divided into 360 parts, as we also sup-pose those in the Heavens. Ptolomy Author of the Almagest ,and many other of the Ancients have observed what space uponthe Earth contains one of these 360 Parts or Degrees, and have foundit to contain 66 \ Miles. Those which succeeded them, willing tosatisfie themselves by their own experience, met by the order ofAlmamon in the Plains of Sanjar , and having taken the height ofthe Pole, they divided into two Troops, the one marching asdirectly as Was possible towards the North, and the other towardsthe South, till the one found the Pole one Degree more, and theother one Degree less elevated; then meeting again at their first sta-tion to compare their Observations, they found the one hadcomputed 5 6j Miles, but the other just 5 6. but they agreed to ac-count 56s for one Degree, so that between the Observations of theAncients, and of these Moderns there is a difference of 10 Miles.

Now Ptolomy having establisli d the bigness of a Degree 500 Sta-dia, for which the Arabs account 66} Miles, it follows that the A-rabian Mile was equal to 7 j Stadia; but we are to seek what Sta-dium Ptolomy means; for if it were the Greek, eight of which madeone ancient Italian Mile, the proportion of the Arabick Mile,so the Italian will be as 15 to 16, and consequently the 56} Milesfound in a Degree by the Arabs , will make but 53F old ItalianMiles. But if more favourably to the Arabs , we suppose ( which

Abulfeditin his Preface.