state depicted in the next diagram (Fig. 7) with reference to Jupiter.
All were to the west, and arranged nearly in the same straight line;
but the satellite which counted third from Jupiter was raised a little
to the north. The nearest to Jupiter was the smallest of all; the
rest appeared larger and in order of magnitude; the intervals between
Jupiter and the three nearest satellites were all equal, and were of
the magnitude of 2´ each; but the satellite furthest to the west was
distant 4´ from the satellite nearest to it. They were very brilliant,
and not at all twinkling, as they have always appeared both before
and since. But at the seventh hour there were only three satellites,
presenting with Jupiter an appearance of the following kind (Fig. 8).
They were, that is to say, in the same straight line to a hair; the
nearest to Jupiter was very small, and distant from the planet 3´; the
distance of the second from this one was 1´; and of the third from the
second 4´ 30´´. But after another hour the two middle satellites were
still nearer, for they were only 30´´, or less, apart.
Jan. 16.—At the first hour of the night I saw three satellites arranged
in this order (Fig. 9). Jupiter was between two of them, which were at
a distance of 0´ 40´´ from the planet on either side, and the third was
west of Jupiter at a distance of 8´. The satellites near to Jupiter
appeared brighter than the satellite further off, but not larger.
Jan. 17, after sunset 0 hours 30 minutes, the configuration was of
this kind (Fig. 10). There was one satellite only to the east, at a
distance of 3´ from Jupiter; to the west likewise there was only one
satellite, distant 11´ from Jupiter. The satellite on the east appeared
twice as large as the satellite to the west; and there were no more
than these two. But four hours after, that is, nearly at the fifth
hour, a third satellite began to emerge on the east side, which, before
its appearance, as I think, had been joined with the former of the two
other satellites, and the position was of this kind (Fig. 11). The
middle satellite was very near indeed to the satellite on the east,
and was only 20´´ from it; and was a little towards the south of the
straight line drawn through the two extreme satellites and Jupiter.
Jan. 18, at 0 h. 20 m. after sunset, the appearance was such as this
(Fig. 12). The satellite to the east was larger than the western one,
and was at a distance from Jupiter of 8´, the western one being at a
distance of 10´.
Jan. 19.—At the second hour of the night the relative position of
the satellites was such as this (Fig. 13); that is, there were three
satellites exactly in a straight line with Jupiter, one to the east, at
a distance of 6´ from Jupiter; between Jupiter and the first satellite
to the west in order, there was an interval of 5´; this satellite was
4´ off the other one more to the west. At that time I was doubtful
whether or no there was a satellite between the satellite to the east
and Jupiter, but so very close to Jupiter as almost to touch the
planet; but at the fifth hour I saw this satellite distinctly, by
that time occupying exactly the middle position between Jupiter and
the eastern satellite, so that the configuration was thus (Fig. 14).
Moreover, the satellite which had just come into view was very small;
yet at the sixth hour it was nearly as large as the rest.
Jan. 20: 1 h. 15 m.—A similar arrangement was seen (Fig. 15). There
were three satellites, so small as scarcely to be distinguishable;
their distances from Jupiter, and from one another, were not more
than 1´. I was doubtful whether on the western side there were two
satellites or three. About the sixth hour they were grouped in this way
(Fig. 16). The eastern satellite was twice as far away from Jupiter as
before, that is 2´; on the western side, the satellite in the middle
was distant from Jupiter 0´ 40´´, and from the satellite still further
to the west 0´ 20´´; at length, at the seventh hour, three satellites
were seen on the western side (Fig. 17). The satellite nearest to
Jupiter was distant from the planet 0´ 20´´; between this one and the
satellite furthest to the west there was an interval of 40´´, but
between these another satellite was in view slightly southward of them,
and not more than 10´´ off the most westerly satellite.
Jan. 21: 0 h. 30 m.—There were three satellites on the east side; the
satellites and Jupiter were at equal distances apart (Fig. 18). The
intervals were by estimation 50´´ each. There was also one satellite
on the west, distant 4´ from Jupiter. The satellite on the east side
nearest to Jupiter was the least of all.
Jan. 22: 2 h.—The grouping of the satellites was similar (Fig. 19).
There was an interval of 5´ from the satellite on the east to Jupiter;
from Jupiter to the satellite furthest to the west 7´. The two interior
satellites on the western side were 0´ 40´´ apart, and the satellite
nearer to Jupiter was 1´ from the planet. The inner satellites were
smaller than the outer ones, but they were situated all in the same
straight line, along the ecliptic, except that the middle of the
three western satellites was slightly to the south of it, but at the
sixth hour of the night they appeared in this position (Fig. 20). The
satellite on the east was very small, at a distance from Jupiter of 5´
as before; but the three satellites on the west were separated by equal
distances from Jupiter and from each other; and the intervals were
nearly 1´ 20´´ each. The satellite nearest Jupiter appeared smaller
than the other two on the same side, but they all appeared arranged
exactly in the same straight line.
Jan. 23, at 0 h. 40 m. after sunset, the grouping of the satellites
was nearly after this fashion (Fig. 21). There were three satellites
with Jupiter in a straight line along the ecliptic, as they always
have been; two were on the east of the planet, one on the west; the
satellite furthest to the east was 7´ from the next one, and this
satellite 2´ 40´´ from Jupiter; Jupiter was 3´ 20´´ from the satellite
on the west; and they were all of nearly the same size. But at the
fifth hour the two satellites which had been previously near Jupiter
were no longer visible, being, as I suppose, hidden behind Jupiter, and
the appearance presented was such as this (Fig. 22).
Jan. 24.—Three satellites, all on the east side, were visible, and
nearly, but not quite, in the same straight line with Jupiter, for the
satellite in the middle was slightly to the south of it (Fig. 23). The
satellite nearest to Jupiter was 2´ distant from the planet; the next
in order 0´ 30´´ from this satellite, and the third was 9´ further off
still; they were all very bright. But at the sixth hour two satellites
only presented themselves to view in this position, namely in the same
straight line with Jupiter exactly, and the distance of the nearest
to the planet was lengthened to 3´; the next was 2´ further off, and
unless I am mistaken, the two satellites previously observed in the
middle had come together, and appeared as one.
Jan. 25, at 1 h. 40 m., the satellites were grouped thus (Fig. 24).
There were only two satellites on the east side, and these were rather
large. The satellite furthest to the east was 5´ from the satellite in
the middle, and it was 6´ from Jupiter.
Jan. 26, at 0 h. 40 m., the relative positions of the satellites were
thus (Fig. 25). Three satellites were in view, of which two were
east and the third west of Jupiter; this one was distant 3´ from the
planet. On the east side the satellite in the middle was at a distance
of 5´ 20´´; the further satellite was 6´ beyond; they were arranged
in a straight line, and were of the same size. At the fifth hour the
arrangement was nearly the same, with this difference only, that the
fourth satellite was emerging on the east side near Jupiter. It was
smaller than the rest, and was then at a distance of 0´ 30´´ from
Jupiter; but was raised a little above the straight line towards the
north, as the accompanying figure shows (Fig. 26).
Jan. 27, 1 h. after sunset, a single satellite only was in view, and
that on the east side of Jupiter in this position (Fig. 27). It was
very small, and at a distance of 7´ from Jupiter.
Jan. 28 and 29.—Owing to the intervention of clouds, I could make no
observation.
Jan. 30.—At the first hour of the night the satellites were in view,
arranged in the following way (Fig. 28). There was one satellite on
the east side, at a distance of 2´ 30´´ from Jupiter; and there were
two satellites on the west, of which the one nearer to Jupiter was
3´ off the planet, and the other satellite 1´ further. The places of
the outer satellites and Jupiter were in the same straight line; but
the satellite in the middle was a little above it to the north. The
satellite furthest to the west was smaller than the rest.
On the last day of the month, at the second hour, two satellites on
the east side were visible, and one on the west (Fig. 29). Of the
satellites east of the planet, the one in the middle was 2´ 20´´
distant from Jupiter; and the satellite further to the east was 0´ 30´´
from the middle satellite; the satellite on the west was at a distance
of 10´ from Jupiter. They were in the same straight line nearly, and
would have been exactly so, only the satellite on the east nearest to
Jupiter was raised a little towards the north. At the fourth hour, the
two satellites on the east were still nearer together, for they were
only 20´´ apart (Fig. 30). The western satellite appeared rather small
in these two observations.
Feb. 1.—At the second hour of the night the arrangement was similar
(Fig. 31). The satellite furthest to the east was at a distance of 6´
from Jupiter, and the western satellite 8´. On the east side there was
a very small satellite, at a distance of 20´´ from Jupiter. They made a
perfectly straight line.
Feb. 2.—The satellites were seen arranged thus (Fig. 32). There was one
only on the east, at a distance of 6´ from Jupiter. Jupiter was 4´
from the nearest satellite on the west; between this satellite and the
satellite further to the west there was an interval of 8´; they were in
the same straight line exactly, and were nearly of the same magnitude.
But at the seventh hour four satellites were there—two on each side
of Jupiter (Fig. 33). Of these satellites, the most easterly was at a
distance of 4´ from the next; this satellite was 1´ 40´´ from Jupiter;
Jupiter was 6´ from the nearest satellite on the west, and this one
from the satellite further to the west, 8´; and they were all alike in
the same straight line, drawn in the direction of the Zodiac.
Feb. 3: 7 h.—The satellites were arranged in the following way (Fig.
34):—The satellite on the east was at a distance of 1´ 30´´ from
Jupiter; the nearest satellite on the west, 2´, and there was a
long distance, 10´, from this satellite to the satellite further to
the west. They were exactly in the same straight line, and of equal
magnitude.
Feb. 4: 2 h.—Four satellites attended Jupiter, two on the east and
two on the west, arranged in one perfectly straight line, as in the
adjoining figure (Fig. 35). The satellite furthest to the east was at
a distance of 3´ from the next satellite. This one was 0´ 40´´ from
Jupiter; Jupiter 4´ from the nearest satellite on the west; and this
one from the satellite further to the west 6´. In magnitude they were
nearly equal; the satellite nearest to Jupiter was rather smaller in
appearance than the rest. But at the seventh hour (Fig. 36) the eastern
satellites were at a distance of only 0´ 30´´ apart. Jupiter was 2´
from the nearest satellite on the east; and from the satellite on the
west, next in order, 4´; this one was distant 3´ from the satellite
further to the west. They were all equal in magnitude, and in a
straight line, drawn in the direction of the ecliptic.
Feb. 5.—The sky was cloudy.
Feb. 6.—Two satellites only appeared, with Jupiter between them, as is
seen in the accompanying figure (Fig. 37). The satellite on the east
was 2´ from Jupiter, and that on the west 3´. They were in the same
straight line with Jupiter, and were equal in magnitude.
Feb. 7.—There were two satellites by the side of Jupiter, and both of
them on the east of the planet, arranged in this manner (Fig. 38).
The intervals between the satellites and Jupiter were equal, and of
1´ each; and a straight line would go through them and the centre of
Jupiter.
Feb. 8: 1 h.—Three satellites were there, all on the east side of
Jupiter, as in the diagram (Fig. 39). The nearest to Jupiter, a
rather small one, was distant from the planet 1´ 20´´; the middle
one was 4´ from this satellite, and was rather large; the satellite
furthest to the east, a very small one, was at a distance of 0´ 20´´
from this satellite. It was doubtful whether there was one satellite
near to Jupiter or two, for sometimes it seemed that there was another
satellite by its side towards the east, wonderfully small, and only
10´´ from it. They were all situated at points in a straight line drawn
in the direction of the Zodiac. At the third hour the satellite nearest
to Jupiter was almost touching the planet, for it was only distant
10´´ from it; but the others had become further off, for the middle
one was 6´ from Jupiter. At length, at the fourth hour, the satellite
which was previously the nearest to Jupiter joined with the planet and
disappeared.
Feb. 9: 0 h. 30 m.—There were two satellites on the east side of
Jupiter, and one on the west, in an arrangement such as this (Fig. 40).
The satellite furthest to the east, which was a rather small one, was
distant 4´ from the next satellite; the satellite in the middle was
larger, and at a distance of 7´ from Jupiter. Jupiter was distant 4´
from the western satellite, which was a small one.
Feb. 10: 1 h. 30 m.—A pair of satellites, very small, and both on the
east of the planet, were visible, in the following position (Fig. 41).
The further satellite was distant from Jupiter 10´, the nearer 0´ 20´´,
and they were in the same straight line; but at the fourth hour the
satellite nearest to Jupiter no longer appeared, and the other seemed
so diminished that it could scarcely be kept in sight, although the
atmosphere was quite clear, and the satellite was further from Jupiter
than before, since its distance was now 12´.
Feb. 11: 1 h.—There were two satellites on the east, and one on the
west (Fig. 42). The western satellite was at a distance of 4´ from
Jupiter. The satellite on the east, nearest to the planet, was likewise
4´ from Jupiter; but the satellite further to the east was at a
distance from this one of 8´; they were fairly clear to view, and in
the same straight line; but at the third hour the fourth satellite was
visible near to Jupiter on the east, less in magnitude than the rest,
separated from Jupiter by a distance of 0´ 30´´, and slightly to the
north out of the straight line drawn through the rest (Fig. 43). They
were all very bright and extremely distinct, but at 5 h. 30 m. the
satellite on the east nearest to Jupiter had moved further away from
the planet, and was occupying a position midway between the planet and
the neighbouring satellite further to the east. They were all in the
same straight line exactly, and of the same magnitude, as may be seen
in the accompanying diagram (Fig. 44).
Feb. 12: 0 h. 40 m.—A pair of satellites on the east, a pair likewise
on the west, were near the planet (Fig. 45). The satellite on the
east furthest removed from Jupiter was at a distance of 10´, and the
further of the satellites on the west was 8´ off. They were both fairly
distinct. The other two were very near to Jupiter, and very small,
especially the satellite to the east, which was at a distance of 0´
40´´ from Jupiter. The distance of the western satellite was 1´. But at
the fourth hour the satellite which was nearest to Jupiter on the east
was visible no longer.
Feb. 13: 0 h. 30 m.—Two satellites were visible in the east, two also
in the west (Fig. 46). The satellite on the east near Jupiter was
fairly distinct; its distance from the planet was 2´. The satellite
further to the east was less noticeable; it was distant 4´ from the
other. Of the satellites on the west, the one furthest from Jupiter,
which was very distinct, was parted from the planet 4´. Between this
satellite and Jupiter intervened a small satellite close to the most
westerly satellite, being not more than 0´ 3´´ off. They were all in
the same straight line, corresponding exactly to the direction of the
ecliptic.
Feb. 15 (for on the 14th the sky was covered with clouds), at the
first hour, the position of the satellites was thus (Fig. 47); that
is, there were three satellites on the east, but none were visible
on the west. The satellite on the east nearest to Jupiter was at a
distance of 0´ 50´´ from the planet; the next in order was 0´ 20´´
from this satellite, and the furthest to the east was 2´ from the
second satellite, and it was larger than the others, for those nearer
to Jupiter were very small. But about the fifth hour only one of the
satellites which had been near to Jupiter was to be seen; its distance
from Jupiter was 0´ 30´´. The distance of the satellite furthest to the
east from Jupiter had increased, for it was then 4´ (Fig. 48). But at
the sixth hour, besides the two situated as just described on the east,
one satellite was visible towards the west, very small, at a distance
of 2´ from Jupiter (Fig. 49).
Feb. 16: 6 h.—Their places were arranged as follows (Fig. 50); that is,
the satellite on the east was 7´ from Jupiter, Jupiter 5´ from the next
satellite on the west, and this 3´ from the remaining satellite still
further to the west. They were all of the same magnitude nearly, rather
bright, and in the same straight line, corresponding accurately to the
direction of the Zodiac.
Feb. 17: 1 h.—Two satellites were in view, one on the east, distant 3´
from Jupiter; the other on the west, distant 10´ (Fig. 51). The latter
was somewhat less than the satellite on the east; but at the sixth
hour the eastern satellite was nearer to Jupiter, being at a distance
of 0´ 50´´, and the western satellite was further off, namely 12´. At
both observations they were in the same straight line with Jupiter, and
were both rather small, especially the eastern satellite in the second
observation.
Feb. 18: 1 h.—Three satellites were in view, of which two were on
the west and one on the east; the distance of the eastern satellite
from Jupiter was 3´, and of the nearest satellite on the west 2´; the
remaining satellite, still further to the west, was 8´ from the middle
satellite (Fig. 52). They were all in the same straight line exactly,
and of about the same magnitude. But at the second hour the satellites
nearest to the planet were at equal distances from Jupiter, for the
western satellite was now also 3´ from the planet. But at the sixth
hour the fourth satellite was visible between the satellite on the east
and Jupiter, in the following configuration (Fig. 53). The satellite
furthest to the east was at a distance of 3´ from the next in order;
this one was at a distance of 1´ 50´´ from Jupiter; Jupiter was at a
distance of 3´ from the next satellite on the west, and this 7´ from
the satellite still further to the west. These were nearly equal in
magnitude, only the satellite on the east nearest to Jupiter was a
little smaller than the rest, and they were all in the same straight
line parallel to the ecliptic.
Feb. 19: 0 h. 40 m.—Two satellites only were in view, west of Jupiter,
rather large, and arranged exactly in the same straight line with
Jupiter, in the direction of the ecliptic (Fig. 54). The nearer
satellite was at a distance of 7´ from Jupiter and of 6´ from the
satellite further to the west.
Feb. 20.—The sky was cloudy.
Feb. 21: 1 h. 30 m.—Three satellites, rather small, were in view,
placed thus (Fig. 55). The satellite to the east was 2´ from Jupiter;
Jupiter was 3´ from the next, which was on the west; and this one was
7´ from the satellite further to the west. They were exactly in the
same straight line parallel to the ecliptic.
Feb. 25: 1 h. 30 m. (for on the three previous nights the sky was
overcast).—Three satellites appeared, two on the east, which were at a
distance of 4´ apart, the same as the distance of the nearer satellite
from Jupiter; on the west there was one satellite at a distance of
2´ from Jupiter. They were exactly in the same straight line in the
direction of the ecliptic (Fig. 56).
Feb. 26: 0 h. 30 m.—A pair of satellites only were present, one on
the east, distant 10´ from Jupiter; the other was on the west, at a
distance of 6´ (Fig. 57). The eastern satellite was slightly smaller
than the western. At the fifth hour three satellites were visible; for,
besides the two already noticed, a third satellite was in view, on the
west, near Jupiter, very small, which previously had been hidden behind
Jupiter, and it was at a distance of 1´ from the planet (Fig. 58).
But the satellite on the east was seen to be further off than before,
being at a distance of 11´ from Jupiter. On this night, for the first
time, I determined to observe the motion of Jupiter and the adjacent
planets (his satellites) along the zodiac, by reference to some fixed
star; for there was a fixed star in view, eastwards of Jupiter, at a
distance of 11´ from the satellite on the east, and a little to the
south, in the following manner (Fig. 59).
Feb. 27: 1 h. 4 m.—The satellites appeared in the following
configuration. The satellite furthest to the east was at a distance
of 10´ from Jupiter; the next in order was near Jupiter, being at a
distance of 0´ 30´´ from the planet. The next satellite was on the
western side, at a distance of 2´ 30´´ from Jupiter; and the satellite
further to the west was at a distance of 1´ from this. The two
satellites near to Jupiter appeared small, especially the satellite
on the east; but the satellites furthest off were very bright,
particularly that on the west, and they made a straight line in the
direction of the ecliptic exactly. The motion of the planets towards
the east was plainly seen by reference to the aforesaid fixed star, for
Jupiter and his attendant satellites were nearer to it, as may be seen
in the accompanying figure (Fig. 60). At the fifth hour the satellite
on the east, near to Jupiter, was 1´ from the planet.
Feb. 28: 1 h.—Only two satellites were visible, one on the east, at a
distance of 9´ from Jupiter, and another on the west, at a distance of
2´; they were both rather bright, and in the same straight line with
Jupiter, and a straight line drawn from the fixed star perpendicular
to this straight line fell upon the satellite on the east, as in the
figure (Fig. 61). At the fifth hour a third satellite was seen at a
distance of 2´ from Jupiter, on the east, in the position shown in the
figure (Fig. 62).
March 1: 0 h. 40 m.—Four satellites, all on the east of the planet,
were seen; the satellite nearest to Jupiter was 2´ from the planet;
the next 1´ from this; the third was 0´ 20´´ from the second, and was
brighter than the others; and the satellite still further to the east
was at a distance of 4´ from it, and was smaller than the others (Fig.
63). They made a straight line very nearly, only the satellite third
from Jupiter was slightly above the line. The fixed star formed with
Jupiter and the most easterly satellite an equilateral triangle, as in
the figure.
March 2: 0 h. 40 m.—Three satellites were in attendance, two on the
east and one on the west, in the configuration shown in the diagram
(Fig. 64). The satellite furthest to the east was 7´ from Jupiter; from
this satellite the next was distant 0´ 30´´, and the satellite on the
west was separated from Jupiter by an interval of 2´. The satellites
furthest off were brighter and larger than the remaining satellite,
which appeared very small. The satellite furthest to the east seemed to
be raised a little towards the north, out of the straight line drawn
through the other satellites and Jupiter.
The fixed star already noticed was at a distance of 8´ from the western
satellite, that is, from the perpendicular drawn from that satellite to
the straight line drawn through all the system, as shown in the figure
given.