44. We may suppose that the inhabitants of Venus will be careful to add
a day to some particular part of every fourth year; which will keep the
same seasons to the same days. For, as the great annual change of the
Equinoxes and Solstices shifts the seasons a quarter of a day every
year, they would be shifted through all the days of the year in 36
years. But by means of this intercalary day, every fourth year will be a
leap-year; which will bring her time to an even reckoning, and keep her
Calendar always right.
[Sidenote: When she will appear on the Sun.]
45. Venus’s Orbit is inclined 3-1/2 degrees to the Earth’s; and crosses
it in the 14th degree of Gemini and of Sagittarius; and therefore, when
the Earth is about these points of the Ecliptic at the time that Venus
is in her inferiour conjunction, she will appear like a spot on the Sun,
and afford a more certain method of finding the distances of all the
Planets from the Sun than any other yet known. But these appearances
happen very seldom; and will only be thrice visible at _London_ for
three hundred years to come. The first time will be in the year 1761,
_June_ the 6th, at 5 hours 55 minutes in the morning. The second 1996,
_June_ the 9th, at 2 hours 13 minutes in the afternoon. And the third in
the year 2004, _June_ the 6th, at 7 hours 18 minutes in the forenoon.
Excepting such Transits as these, she shews the same appearances to us
regularly every eight years; her Conjunctions, Elongations, and Times of
rising and setting being very nearly the same, on the same days, as
before.
[Sidenote: She may have a Moon although we cannot see it.]
46. Venus may have a Satellite or Moon, although it be undiscovered by
us: which will not appear very surprising, if we consider how
inconveniently we are placed for seeing it. For it’s enlightened side
can never be fully turned towards us but when Venus is beyond the Sun;
and then, as Venus appears little bigger than an ordinary Star, her Moon
may be too small to be perceptible at such a distance. When she is
between us and the Sun, her full Moon has it’s dark side towards us; and
then, we cannot see it any more than we can our own Moon at the time of
Change. When Venus is at her greatest Elongation, we have but one half
of the enlightened side of her Full Moon towards us; and even then it
may be too far distant to be seen by us. But if she has a Moon, it may
certainly be seen with her upon the Sun, in the year 1761, unless it’s
Orbit be considerably inclined to the Ecliptic: for if it should be in
conjunction or opposition at that time, we can hardly imagine that it
moves so slow as to be hid by Venus all the six hours that she will
appear on the Sun’s Disc.
[Sidenote: The Earth.
Fig. I.