66 CHAPTER VI.
HALF-HOURS WITH THE PLANETS 74 CHAPTER VII.
HALF-HOURS WITH THE SUN AND MOON 93 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.