24 NATURE STUDY. 
is Polaris, the north or pole star. If the observer will watch this 
star from night to night and from hour to hour throughout the 
same night, he will find that the other stars circle round Polaris 
while the latter remains stationary. He will also discover that 
Cassiopeia is not found in exactly the same place in the sky on 
successive evenings at any given time of observation. The 
cause of this will be discussed in a future article. If now, while 
the observer’s gaze is fixed on Polaris, he will swing around to 
the northwest, keeping his gaze at the same altitude, he will see 
a large group of brilliant stars in the shape of a dipper with the 
handle extending upward. This is so prominent and striking a 
group that it seems impossible to mistake it. This group is 
called the “ Great Dipper ” and is the principal one in the con¬ 
stellation Ursa Major, or Great Bear. - The two lower ones 
of this group, it will be observed, lie in a line with Polaris, 
and, if observed on different nights, or throughout the same 
night, those three stars will always be found in he same rela¬ 
tive position, i. e., very nearly in the same straight line. For 
this reason those two stars of the dipper are called “the poin¬ 
ters ” because they point toward the north star. The knowl¬ 
edge of this fact is often of great value to travelers, sportsmen, 
and surveyors, as it enables them to determine the cardinal 
points of the compass and so make their way with safety and 
certainty. 
It will be necessary to have some elementary knowledge of 
circular measure in order to locate satisfactorily many of the 
other stars and star groups ; and so we will just state here 
what every reader probably already knows, viz , that the arc of 
a circle in the sky from the horizon to the zepith is 90°, being 
just a quarter of a circle, which contains exactly 360°. As a 
convenient unit of measure for future comparisons we will state 
that the distance between “ the pointers ” mentioned above, is 
almost exactly five degrees. 
The stars thus far mentioned, and in fact, nearly all the stars 
that meet the observer’s gaze, are called “fixed stars” because 
they do not change their positions relative to each other, i. e., 
they are fixed, or permanent in their relative positions. Forex- 
