Note 43 — Chapter XX

Roughly estimating from the date here given, it seems probable that the line here mentioned refers to the diameter of the earth. Although that diameter had not been exactly measured at that time, a long step toward this had been taken by Picard of France, who in 1671 made the first really valuable measure of the arc of a meridian, a measure which Isaac Newton used in verifying his idea of gravitation. The ambiguous manner in which the line is mentioned by the writer (supposedly Kino, as cited by Diaz) was probably due to cautious dread lest ecclesiastical penalties be visited on the too definite statement of scientific discoveries; for at that time Mexico was dominated by the Inquisition, by which tribunal the great Galileo had been imprisoned less than fifty years before Kino made these observations. The course of this comet can easily be verified, after making due allowance for the precession of the equinoxes, on any map of the constellations. Information for this note is furnished by Albert S. Flint, astronomer of Washburn Observatory, University of Wisconsin.