EASY STAR INTRODUCTION. Ir is very pleasant to know the stars-to be able, like Milton's hermit, to "Sit and rightly spell Of every star that heaven doth show." And it is not at all difficult to learn all the chief star-groups,or constellations, as they are called,-if only the learner goes properly to work. Perhaps I ought rather to say, if the teacher goes properly to work. I remember, when I was a boy about twelve years old, being very much perplexed by the books of astronomy, and the star-charts, from which I tried to learn the stars. There was "Bonnycastle's Astronomy," with a very pretty picture of one constellation,-Andromeda, -in which, if one looked very carefully, one could perceive stars, though these were nearly lost in the carefully shaded picture of the Chained Lady herself. Another book which I found in my father's library showed a series of neat pictures of all the chief constellations, but gave no clear information as to their whereabouts. And the charts which I found were not at all easy to understand, being, in fact, the usual star-charts, which give no information whatever about the places of star-groups on the sky of any place or at any time. So that it was only by working my way from the Great Bear to constellations close by it, then to others close by these, and so on, that I slowly learned the chief star-groups. The object of the series of maps in this little book is to remove this difficulty for young astronomers. The maps are arranged in sets of four, shewing what stars can be seen towards the north, towards the south, towards the east, and towards the west, at a certain convenient hour during every night in the year. This hour varies, night by night. On January 1st, the hour at which the stars shown in the first four maps can be seen in the position shown, will be a quarter past nine in the evening; on January 2, about eleven minutes past nine; on January 3, about seven minutes past nine, and so on, earlier and earlier each night; on January 5, at nine; January 8, at a quarter to nine; January 12, half-past eight; January 16, a quarter past eight; January 20, eight o'clock; January 23, a quarter to eight; January 27, half-past seven; and January 31, a quarter past seven; and so forth. The black part of each map shows the sky as it would be seen by observers living in latitude 40° north, Great Britain, North America and all countries between latitudes 25° and 60° north. This is nearly correct (quite sufficiently so for the purpose of these maps). The United States range in latitude from about 52° to 49° north, and the British Isles from 50° to 59°, an entire range of about 34°; but by far the greater portion of the population of the United States and Canada on one side of the Atlantic, and of the British Isles and the chief European States on the other, occupies the region between the latitudes of New Orleans and Glasgow, say 30° and 56° north latitude. The latitude 40° north is a convenient mid-latitude for the entire range. Maps constructed for that latitude-at least maps intended only to teach young astronomers the constellations-serve quite as well for all latitudes within 15° or 20° on either side of 40°. Only it is necessary to indicate where the horizontal line lies for each limiting latitude, and for one or two intermediate latitudes. Not only, too, are such maps serviceable in that way over a wide range of latitude, but they serve also to illustrate how changes in the observer's latitude affect the aspect of the heavens as seen from the place of observation. The effects of such changes are indeed |