256 JOURNEY FROM actual circumference of the gulf of the Greater Syrtis may be estimated at four hundred and twenty-two geographic miles, and its diameter at two hundred and forty-six * : so that it would be necessary to alter both the circumference and diameter given by Strabo before any use could be made of his dimensions ; and then the measurements must be taken on the authority of the commentators, since they would be no longer those of the geographer. In short, the difficulty appears to be scarcely surmountable ; for though it is evident that the passage is not as Strabo left it, we have no sufficient data for deciding what it really was originally -j-. The measurements given by Pliny are somewhat nearer the truth ; indeed his diameter of the gulf may be considered as remarkably accurate ; for it is stated at three hundred and thirteen Koman miles, equal to two hundred and forty-eight and a quarter geographic miles, and there is consequently no more than two miles and a quarter difference between these dimensions and the actual diameter. His circumference, however, is not by any means so accurate ; it is given at six * This estimate of the ciixumference is deduced from the camel-track, corrected by observations ; and the accuracy to which this mode of computation may be brought by care and attention, and by making the proper allowances, will be seen in the examples which we shall hereafter submit of it.

t If, however, we take the measurements just quoted from the second book of Strabo, as those which he intended to be received in the present case, we shall find that the 4280*0 miles, resulting from the 5000 stadia of Eratosthenes, come very near the truth. The other measurements, however, are far from correct. It will be observed that the diameter given in this place is the same with that mentioned in the second book (1500 stadia).

I Inde Syrtis Major, circuitu DCXXV. aditu autem, CCCXIII, M. Passuum. — Nat.

Hist. lib. V. cap. 4.