In the northern hemisphere the longest day of this year is the 20th
of this month; though in many places it would be difficult to notice
that there was really any difference between the length of this day and
that of a few of those preceding and succeeding. The sun has reached
his farthest point northward, and, although he travels about his usual
distance each day, he moves in a part of his orbit which is, for all
practical purposes, parallel to the equator, and hence must rise about
the same place and hour each morning, and set at the same place and
hour every evening. About the 21st of December of each year we have
the shortest day, with several of the neighboring days but very little
longer; for the reason that at that date the sun reaches its southern
limit and moves almost parallel to the equator.
It may be interesting to see how our neighbors fare in regard to longest
days. By the working of a few problems in spherical trigonometry we find
that our friends living on the equator have all their days the same
length, namely, twelve hours. So that there is in that region no looking
forward to the long winter evenings, nor any hoping for the shortening of
summer’s sultry days. They have, however, this advantage: If the sun’s
rays do sometimes “come down by a straight road,” they do not continue so
long at a time as with us. As we proceed north, we find in latitude 30°
48′ that the longest day is fourteen hours, in latitude 49° 2′, sixteen
hours; in 58° 27′, eighteen hours; in 63° 23′, twenty hours; in 65° 48′,
twenty-two hours; in 66° 32′, twenty-four hours, no night at all; and
51′ further north, that is, in latitude 67° 23′, the longest day begins
about the fifth of June, and lasts till about the fourth of July, and is
about thirty days long; in 73° 40′, it is three months long; in 84° 5′,
it is five months; and at the north pole six months. Practically the days
are longer than here represented; for we have natural light enough to
pursue most vocations both before sunrise and after sunset. In latitude
63° 23′, for example, where the day’s extreme length is twenty hours, on
account of the twilight the remaining four hours might as well be called
daylight, for the sun descends only a few degrees below the horizon, and
though hidden from sight, still through the medium of the atmosphere
affords almost the usual light of day.
Of course our friends in the corresponding latitudes of the southern
hemisphere are enjoying correspondingly short days and long nights.
In 63° 23′ south latitude the day is only four hours long, and the
night twenty hours. No wonder people sometimes say, “This is a queer
world.” Its mechanism is certainly very wonderful. If we wished to be
somewhat exact, we would say that the sun enters _Cancer_ and summer
begins on June 20th, at 7:51 p. m., Washington mean time, and continues
ninety-three days, fourteen hours twenty-two minutes. Other items are as
follows: On the 1st, 15th, and 30th, the sun rises at 4:31, 4:28, and
4:29 a. m.; and on the same dates sets at 7:24, 7:32, and 7:34 p. m.
During the month our days vary in length from fourteen hours fifty-three
minutes to fifteen hours five minutes; and on the 20th, the time from
early dawn till the end of twilight is nineteen hours thirty minutes.
On the 3rd, at 4:00 p. m., the sun is in conjunction with Saturn; on
the 14th, at 3:00 p. m., 90° west of Uranus; on the 30th, at midnight,
farthest from the earth; greatest elevation, in latitude 41° 30′ north,
71° 57′. Diameter decreases from 31′ 36″ on the 1st, to 31′ 32″ on the
30th.