While Mercury is one of the five planets that can be seen with the
naked eye, it must be confessed that he does not play any important
part in the great spectacle of nature as we see it in the skies. But in
a certain way this only adds to our interest in him. The very rarity of
his appearances and the difficulty of finding him give a zest to the
search, and a sense of achievement, when it is successful, that one
does not have with regard to the other planets. It is something akin to
the feeling one has when, after a long tramp to some secluded recess in
the woods in search of the shy pink lady’s slipper, a splendid specimen
of that lovely flower suddenly comes into view hanging gaily on its
stalk, ready for the use of whatever fairy foot may tread its shady
groves.
Then, too, the spring o’ the year is the most likely time to see
Mercury in the evening sky. He comes into his best position for this
view of him just when the evenings are growing longer and milder and
one begins to hunger for outdoor things, so that the quest of him at
that time has the gladness that goes with our first excursions into the
open after a winter’s housing, whether it be in search of flowers, or
birds, or stars, or simply the general loveliness of everything that
belongs to the beginning of the outdoor season.
The reason Mercury is so elusive is that he is always very near the
sun, and in consequence his light is dimmed by the brighter light shed
by that luminary until it is well below the horizon; and after the
sun has set, the planet is so involved in the usual haziness of the
atmosphere near the horizon that the conditions must be very favorable
in order to see him. Though there are recorded observations of Mercury
as far back as nearly three hundred years before Christ, yet some of
the older of the modern astronomers, before the days of the perfected
telescope, are said not to have seen him at all; and the most important
observations of the planet nowadays are made in broad daylight, when
it is higher up in the skies and free from the mists of the horizon.
This can be done by means of a powerful telescope, because it is
possible in this way to shut off the light of surrounding bodies;
but, of course, the conditions are not as favorable as if midnight
observations could be made. Still, if one knows just when and where to
look, Mercury can be seen with the naked eye at least once or twice a
year, and sometimes oftener than this, especially if one chances to
live in one of the Western States, where the air is very clear and the
situation in latitude and altitude more favorable than, say, in New
England, or in the middle Atlantic States. In our Northern States, and
in the whole of England, this planet is more difficult to see, because
of the longer twilight in northern latitudes, and also because the line
of the ecliptic, over which it passes, seems there lower down in the
skies, while in the far South, say in Cuba or Porto Rico, the twilight
is shorter, the ecliptic runs high in the sky, and the situation is
favorable for a good view even though the atmosphere is no clearer than
it is farther north.