DESCRIPTION OF PLATES.


PLATE I.--_Frontispiece._

This plate presents the aspect of the heavens at the four seasons, dealt
with in Chapters II., III., IV., and V. In each map of this plate the
central point represents the point vertically over the observer's head,
and the circumference represents his horizon. The plan of each map is
such that the direction of a star or constellation, as respects the
compass-points, and its elevation, also, above the horizon, at the given
season, can be at once determined. Two illustrations of the use of the
maps will serve to explain their nature better than any detailed
description. Suppose first, that--at one of the hours named under Map
I.--the observer wishes to find Castor and Pollux:--Turning to Map I. he
sees that these stars lie in the lower left-hand quadrant, and very
nearly towards the point marked S.E.; that is, they are to be looked for
on the sky towards the south-east. Also, it is seen that the two stars
lie about one-fourth of the way from the centre towards the
circumference. Hence, on the sky, the stars will be found about
one-fourth of the way from the zenith towards the horizon: Castor will
be seen immediately above Pollux. Next, suppose that at one of the hours
named the observer wishes to learn what stars are visible towards the
west and north-west:--Turning the map until the portion of the
circumference marked W ... N.W. is lowermost, he sees that in the
direction named the square of Pegasus lies not very high above the