Note 11 — Chapter VI

Mercury is best seen when in quadrature to the sun, but not (as I have seen stated) at those quadratures in which he attains his maximum elongation from the sun. This will appear singular, because the maximum elongation is about 27°, the minimum only about 18°. But it happens that in our northern latitudes Mercury is always south of the sun when he attains his maximum elongation, and this fact exercises a more important effect than the mere amount of elongation.