"I examined some things in that hemisphere very diligently, which enables me to contradict the opinions of philosophers. Among other things, I saw the rainbow--that is, the celestial arch--which is white near midnight. Now, in the opinion of some, it takes the color of the four elements: the red from fire, the green from the earth, the white from the air, and blue from the water. Aristotle, in his book entitled _Meteors_, is of a very different opinion. He says: 'The celestial arch is a repercussion of the sun's rays in the vapors of the clouds where they meet, as brightness reflected from the water upon the wall returns to itself. By its interposition it tempers the heat of the sun; by resolving itself into rain it fertilizes the earth, and by its splendor beautifies the heavens. It demonstrates that the atmosphere is filled with humidity, which will disappear forty years before the end of the world, which will be an indication of the dryness of the elements. It announces peace between God and man, is always opposite the sun, is never seen at noon, because the sun is never in the north.'
"But Pliny says that after the autumnal equinox it appears every hour. This I have extracted from the _Comments of Landino_ on the fourth book of the _Æneid_, and I mention it that no man may be deprived of the fruits of his labors, and that due honors may be rendered to every one. I saw this bow two or three times; neither am I alone in my reflections upon this subject, for many mariners are also of my opinion. We saw also the new moon at mid-day, as it came into conjunction with the sun. There were seen also, every night, vapors and burning flames flashing across the sky. A little above, I called this region by the name of hemisphere, which, if we would not speak improperly, cannot be so called when comparing it with our own. It appeared to present that form only partially, and it seemed to us speaking improperly to call it a 'hemisphere.'
"As I have before stated, we sailed from Lisbon--which is nearly forty degrees distant from the equinoctial line towards the north--to this country, which is fifty degrees on the other side of the line. The sum of these degrees is _ninety_, and is the fourth part of the circumference of the globe, according to the true reckoning of the ancients. It is therefore manifest to all _that we measured the fourth part of the earth_.[13]