On account of the necessarily diminutive scale of the charts, everything has been omitted from them which did not seem essential. But for the purpose in view they gain by this process of exclusion, for with more details they would have been confusing. It is the broad, general aspect of the sky with which the beginner must first familiarize himself. At the start the heavens appear to him to be filled with an innumerable multitude of scintillating sparks, scattered everywhere in disorder. But with a little attention he perceives that there is discipline in this host, and immediately the discovery gives him pleasure and awakens his admiration, as the perception of order always does. The great leaders of the firmament come forth, unmistakable, plainly recognizable, and thereupon the rank and file fall into their places. Then the ineffable beauty of the whole assemblage bursts like a revelation upon the mind. This revelation is not for the dull in spirit, but he who has once had it becomes henceforth, and even in spite of previous prejudice or indifference, a devotee of the stars, with a zeal flaming brighter with every swing of the pendulum of his years. In the four circular charts representing the aspect of the heavens respectively at the Vernal Equinox, the Summer Solstice, the Autumnal Equinox, and the Winter Solstice, few stars fainter than the fourth magnitude are included, and not all even of that magnitude, because the sole purpose is to enable the beginner to recognize the constellations by their characteristic groupings of stars and their relative situations in the sky. The insuperable difficulty is to picture the _hemispherical_ sky on a _flat_ page. A certain amount of distortion cannot be avoided, and the reader’s imagination must supply the effect of perspective. He must always remember that the centre of the chart stands for the middle of the sky _overhead_, and that the circular boundary represents the full round of the horizon, from east through south, west, and north, to east again. If he is comparing the chart with the sky while facing south, he should hold the chart upright as it is printed in the book; if he makes the comparison while facing north, he should turn the chart upside down. If he lies on his back with his head to the north (and in no other way can one get so vast an impression of the starry dome), and holds the chart over his head, it will represent the entire vault of the firmament.