第17章

On the 8th of January, being in the latitude of 30 degrees 25 minutes south, and in the longitude of 192 degrees 20 minutes, we observed the variation of the needle to be 90 degrees towards the east, and as we had a high rolling sea from the south-west, I conjectured there could not be any land hoped for on that side. On the 12th we found ourselves in 30 degrees 5 minutes south latitude, and in 195 degrees 27 minutes of longitude, where we found the variation 9 degrees 30 minutes to the east, a rolling sea from the south-east and from the south-west. It is very plain, from these observations, that the position laid down by Dr. Halley, that the motion of the needle is not governed by the poles of the world, but by other poles, which move round them, is highly probable, for otherwise it is not easy to understand how the needle came to have, as our author affirms it had, a variation of near 27 degrees to the west, in the latitude of 45 degrees 47 minutes, and then gradually decreasing till it had no variation at all; after which it turned east, in the latitude of 42 degrees 37 minutes, and so continued increasing its variation eastwardly to this time.