Page:The Philippine Islands, 1493-1803 (Volume 01).djvu/206

 and wet or dry; whether the day's run is estimated from the poop, prow, or amidships; and other special considerations that I pass by, such as the heaviness or lightness of the winds, the differences in compasses, etc. From the above then, I infer that it is difficult and unsatisfactory to determine the size of the earth by means of measuring it by traveling or sailing, and the same was maintained by Ptolemæus and other erudite men by actual test.

As to the second method, namely, by determining what portion of the earth corresponds to another known part of the heavens, it is more probabile etiam per demonstrationem. But the difficulty of this method lies in the fact that this proof or demonstration has been made by many learned and experienced men, and we discover a great diversity in their results, as I pointed out in my opinion when it was agreed that every one should commit in scriptis the number of leagues corresponding to each degree, of which the following is a copy.

[Here follow the different calculations of the length of a degree and the circumference of the earth, beginning with Aristotle. Briefly these are as follows: Aristotle, 800 stadia to a degree, making the terrestial circumference, 12,500 leagues; Strabo, Ambrosius, Theodosius, Macrobius, and Eratosthenes, each 700 stadia to the degree, and a circumference of 7,875 leagues; Marinus and Ptolemæus, 500 stadia to the degree, and a circumference of 5,625 leagues;