did not diſcover that the two places lay under different meridians. The numbers of Eratoſthenes above ſpecifed were not however acquieſced in by ſucceeding aſtronomers, ſince Marinus and Ptolemy allotted, as Dr. Blair obſerves, no more than 3600 ſtadia[1] to that diſtance; as the ſeven degrees twelve minutes (a calculation of the latitude not very different from that of Mr. D'Anville before-mentioned) amounted exactly to that number on the proportion of 500 ſtadia to a degree; which, Ptolemy tells us, was agreeable to menſurations allowed and acknowledged.
The learned Prelate's calculations in the next paragraph are rather incorrect. He States the proportion of the Roman foot to the Engliſh to be as 97: 100; whereas it appears from Greaves, whoſe meaſurement the Biſhop ſeems to have adopted, to be only 967: 1000; which makes a difference of nearly 1134 part, and amounts nearly to 16 feet in the ſpace of an Engliih mile; which, although an inconſiderable difference in ſmall diſtances, is neceſſary to be taken into account in the eſtimation of large extents; and this error, by over-rating the length of the Roman foot, vitiates in ſome meaſure his ſubſequent calculations.
This appears in the next ſentence of his Lordſhip's obſervations; where he urges, "that if eight Olympic ſtadia were equal to a Roman mile, and that Polybius's addition of ⅓ of a ſtadium was an error of his own, ariſing from the difference between the Roman and the Olympic foot, then one Olympic ſtadium would be 506.25 feet, London meaſure;" which computation over-rates
- ↑ 3600 × 50 gives only 180,000 ſtadia, or 20603.4 Engliſh miles, for the circumference of the earth.
