TO KNOW THE STARRY HEAVENS 
21 
constellation Scorpio (the scorpion) 
with its bright reddish star Antares. 
Next above this are Ophiuchus (the 
serpent holder) and Serpens (the ser- 
pent which he is holding). In this case 
we have one constellation crossing an- 
other. Just south of the zenith is Her- 
cules, the kneeler, upside down as we 
see him, with his head toward the head 
of Ophiuchus and his foot resting on 
the head of Draco, the dragon. Her- 
cules holds a branch in his left hand 
in which serpents are entwined. Draco 
is one of the circumpolar constellations 
which may be seen nearly at all times 
but is in its best position this month. 
It will be seen to make a semicircle 
about the little dipper, Ursa Minor, and 
then turn and end in a diamond-shaped 
head just north of Hercules. This ar- 
rangement of men and serpents in these 
constellations can scarcely be acciden- 
tal. No theory as to the reason for the 
arrangement is well established. At- 
tempts have been made to trace the 
story of the Garden of Eden in these 
constellations. 
The Planets. 
The positions of Jupiter and Saturn 
are marked on the map. This is the 
last month in which they may be seen 
well. Venus is a brilliant morning star. 
It is at its greatest western elongation 
July i. It may be seen in the east be- 
fore sunrise. Mercury is similarly at its 
greatest western elongation July 28. 
On July 4 the earth is at the point of 
its orbit farthest from the sun. At this 
time the earth is about 3,000,000 miles 
farther from the sun than in January. 
In order to show the nature of the 
earth’s motion the orbit of the earth is 
usually represented as an ellipse in 
which the flattening is much exagger- 
ated. The real orbit of the earth is so 
nearly a true circle that if accurately 
represented in a figure a very minute 
examination would be necessary to 
show the departure from a true circle. 
The boundary of the map in Figure 1 
is a true circle. If the earth’s orbit were 
represented by this circle the repre- 
sentation would be accurate to about 
one-thousandth of an inch. 
The moon in its path among the stars 
always hides the stars behind it. At 
times it passes between us and some of 
the brighter stars — occults them, as as- 
tronomers term it. Two such occupa- 
tions occur this month. On July 
19 Rho Sagittarii disappears behind the 
moon at 3:11 A. M. as seen from Wash- 
ington and at nearly that time else- 
where. It remains hidden forty-one 
minutes. On July 30 Delta Tauri is 
similarly occulted. This occupation be- 
gins at 4:08 A. M. and lasts seventy 
minutes. 
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Do the Stars Move? 
Do the stars move ? Whatever is 
meant by the question the answer is 
yes. Our map, Figure 1, shows the posi- 
tions of the stars at 9 P. M. July 1, for 
a latitude of forty-five degrees north. 
Change any of these factors and the 
appearance of the sky will be different. 
The earth rotates on its axis, carrying 
the observer with it. once in a day ; 
hence everything not on the earth will 
appear to move in the opposite direc- 
tion just as the scenery appears to move 
when riding in a train. For this reason 
the stars appear to rotate from east to 
west as though fixed on a great sphere 
whose axis is that of the earth. This 
axis of rotation of the sky is now near 
the north star. For this reason the stars 
are not in the same position at different 
times of the night. Then, too, the earth 
moves about the sun. As the direction 
of the sun changes due to the earth’s 
revolution about it so does the direction 
opposite to the sun change and this is 
the direction in which we see stars ; that 
is, at night. Hence as we are looking in 
a different direction at night at different 
times of the year we see different stars. 
For this reason the stars we see at 9 
P. M. July 1 are not the same as those 
we see at the same time August 1. On 
August 1 at seven o’clock they will be 
in the same positions as they were at 
9 P. M. July 1, for in a month the earth 
has moved one-twelfth of the way 
around in its orbit, a month being one- 
twelfth of a year, and one-twelfth of 
the twenty-four hours, the time of the 
earth's rotation, being two hours. 
These are the large changes in the po- 
sitions of the stars and the only ones 
considered in the map for a fixed lati- 
tude. Anything which changes the po- 
sition of the observer relative to the 
stars will change their apparent po- 
sitions. 
The next most important motion of 
the earth is a gradual change in the 
direction of the axis of the earth. Much 
as a spinning top changes the position 
of its axis of rotation so the rotating 
