the pole-star is found, and for the purpose of such
observations as are here considered, this star may be looked upon
as marking the exact direction of the north.

Perhaps nothing further is required; but if the observer prefer it
he can determine the north point conveniently _at noon_ by setting
up a vertical stick in the sunlight and noting the direction in which
the shadow lies. Once the observation has been made, he can note what
objects (these should be distant) lie towards the different points
of the compass, and from that time he can use the accompanying maps
without any reference to the Great Bear and the Pointers.

It is worth noticing that the stars called the Guardians of the
Pole form no bad time-piece when used with the aid of such maps
as the present. They revolve round the pole once in twenty-four
hours (less about four minutes), in a direction contrary to that of
a clock's hands. But stars near the equator, whose motions are much
more rapid, afford a yet better measure of time, if the direction
of the south point is well determined.

Of course, the observer who really wishes to become an astronomer
will not rest satisfied by learning only the principal stars shown
in these maps. By means of the regular star-maps, such as those
of my School Star Atlas, he will be able to explore the depths
of all the constellations, having once learned their position and
general appearance from the accompanying maps. It will be well for
the student to remember that the planets Venus, Mars, Jupiter, and
Saturn will at times appear among the constellations here shown.
Venus and Jupiter can always be recognized by their superior light,
Mars and Saturn by the steadiness with which they shine. The almanac
will always show when these planets and Mercury (often very bright
in the clear skies of America) are above the horizon, and where
they are situate. They never appear except among the zodiacal
constellations.

For particulars and pictures of the different constellations, and
other details associated with the study of the star-groupings,
the reader is referred to my "Easy Star Lessons," published like
the present maps by Messrs. PUTNAM'S SONS. I have to thank the
proprietors of the _Scientific American_ for permission to publish
these maps, which originally appeared (though in a slightly different
form) in the pages of that excellent magazine. The Latin names
of the constellations included in the maps of this series are a