compare them with the sky at other places in the same latitude, say in North America, Northern Germany, or even in Asia, it must be at the local midnight of each station. Or, if we desire to make a similar comparison with the southern sky for different places, it must also be at the local midnight of each locality. Let us take as an example the February diagrams of the southern sky, which correspond strictly with the heavens on February 15th at midnight, Cape mean time. Here the landscapes are views of two stations in Cape Colony, but an observer in Australia would have seen exactly the same stars above the horizon at his local midnight, which occurred eight or nine hours before. In this interval of time, the Earth has turned on its axis a distance corresponding exactly to the difference of longitude between the two countries. Wherever the reader of these pages is situated, therefore, no confusion need arise in his mind on this ground, for he has only to consider that the diagrams represent the heavens at his own midnight, whatever longitude his station may be, on the parallels of 51° 30′ north latitude, and 34° south latitude respectively. In Great Britain, Greenwich mean time, determined daily at the Royal Observatory by the observations of the transits of standard stars over the meridian, or railway time, as it is more commonly called, is now so universally kept in all parts of the country, owing to the extension of the railway system into its remotest corners, that the great majority of people know little or nothing of their own local time, as indicated by the culmination of the Sun. The adoption of a universal clock-time has been acknowledged on all sides to be a valuable contribution to the order and punctuality of the nation, without any corresponding drawback being produced on domestic interests by the difference of longitude between the extreme eastern and western coasts, which does not, at the greatest, exceed half-an-hour. If our diagrams were consulted in the Land's End district of Cornwall, the time selected for the comparison should be twentythree minutes past twelve, railway time. For ordinary purposes, it would not be convenient to adopt a universal time for different countries; for if Greenwich mean time were kept all over the globe, although some advantages might occasionally be derived by the mariner for nautical purposes, the ordinary civil days would begin and end so contrary to all our notions of common sense, and so antagonistic to the natural day of the place, that endless confusion in the daily habits of the people would be the consequence. Every civilised country, therefore, has generally its own local or national time, referred in most cases to that of the metropolis, or of the city or town where the principal observatory of the nation is situated. In large and thinly-populated countries, where, in the absence of railways, intercommunication is difficult, the local time of the chief town of each province or district is frequently adopted. In Great Britain, as stated above, the standard Greenwich mean time, communicated daily from the Royal Observatory to all parts of England by means of the telegraph wires in connection with that establishment. Irish time-the same as Dublin time-is used throughout our sister island, even to the westernmost coasts of Kerry. The whole of France keeps Paris is INTRODUCTORY AND EXPLANATORY. time; Germany keeps Berlin or Vienna time; northern Russia, St. Petersburg or Pulkowa time; the United States of America, Washington, New York, or Boston time, and so on. In like manner, in the southern hemisphere, at the Cape of Good Hope there is Cape time; in Australia there is probably Sydney, Melbourne, or Adelaide time, as the case may be. It can thus be easily perceived that, after the diagrams of the southern hemisphere have served their purpose as guides to the star-watcher at an Australian midnight, they will, eight or nine hours afterwards, be equally available for a Cape of Good Hope midnight, the configurations of the stars being seen in both places under exactly similar circumstances. A few brief general explanations of the maps are requisite. In comparing the diagrams with the sky, the observer is supposed to be looking either due north or south along the exact meridian of his station. This position is absolutely necessary; for the apparent aspect of the constellations is different if the face be turned aside from the true plane of the meridian towards the south-west or south-east, north-west or north-east. One of the first objects to consider, therefore, is to be certain that the direction of the imaginary meridian line is approximately known. This may be done by several methods. In the day-time it can be determined by noticing the exact time when the Sun is on the meridian. As this takes place generally some minutes before or after ordinary local noon, reference must be made to the calendar of any almanack in which this difference is usually inserted. The moment when the Sun is in this position, it is at the highest point in the heavens, or on the meridian. At night, the same can be done by observing the Moon on the meridian, the time of which is also given in most almanacks. But the most useful method of all, because it may be adopted at any instant during the night hours, is by first finding the North Pole, indicated approximately by the position of Polaris, or the Pole star. This well-known fixed star can be easily detected by using the first two stars in the principal group of the constellation Ursa Major, as pointers, and is so near the celestial pole that, for all practical purposes of this kind, it may be assumed to be a stationary object. When the observer has identified Polaris, all he has to do is to draw an imaginary line in his mind from the pole to the zenith, and thence to the south horizon, and he has determined the meridian line* of his station sufficiently well for the comparison of the diagrams with the heavens. Each of the star-views represents the sky included between the zenith and the north or south horizon, according as the observer is looking north or south. Practically this is more of the heavens than the eye can grasp at any one time, for the stars situated in and near the zenith cannot be seen without a special effort of the observer. As the celestial vault is spherical, it is very difficult to represent its appearance efficiently on a flat surface without considerable distortion of the constellations in some directions. There The word meridian is derived from the Latin meridies, mid-day, because when the Sun is in that position there is noon at all places of the same longitude as that where it is situated in the zenith. The term meridian may, however, be more exactly defined as a great circle of the celestial sphere passing through the zenith and the poles. are several methods of constructing celestial maps, but there is not one in which the constellations are free from distortion, either more or less. In the projection adopted in the formation of this series of diagrams, this distortion takes place near the horizon, but not in the central part of the map. Partly for this reason, but chiefly because the scale of the diagrams would become far too small for the easy identification of the different objects, the sky low down in the east and west has been omitted. When, however, stars of superior magnitude are visible in the east and west out of the range of the maps, their positions are generally pointed out in the monthly descriptions, so that it will not be a difficult task for our youngest reader to identify them. The positions of the Moon and planets cannot of necessity be inserted, on account of the varying and peculiar character of their movements. If the upper parts of the two monthly diagrams be joined together, the heavens from the south horizon to the north horizon will be represented. The reader is therefore requested to bear in mind that the upper boundary lines are due east and west, passing through the zenith, or the point in the heavens directly over-head, and that the meridianline divides the diagrams into two equal portions. The central part of each is therefore on the meridian, about forty-five degrees from the zenith. Every star down to the fifth magnitude is inserted in the diagrams looking south; the northern diagrams contain all stars down to the fourth magnitude, and in some of the constellations to the fifth. The addition of many more small stars would only tend to produce confusion, without being of any practical benefit to the reader. The interest of most non-telescopic star-gazers is principally centred in those stars only which are prominent objects and easily to be distinguished. The reader will find the index-maps a considerable assistance to him for the proper elucidation of the large diagrams, independently of the descriptive explanatory notes. In the preparation of the index-maps, care has been taken to include all the large stars of the first and second magnitudes, and many of the third. By the aid of these supplementary maps, every important star can, with very little trouble, be directly identified, not only in the large maps, but also in the heavens itself. The descriptive notes for each month must be considered complete in themselves, without reference to those in any other month, unless specially mentioned. For this reason, we have found it occasionally necessary to include a few remarks which involve a repetition of what has been given in a preceding month. The apparent changing positions of the stars, with respect to the zenith and horizon in different seasons of the year, cannot fail to attract the notice of the most superficial observer. In the descriptive notes for March, the cause of these seasonal changes is briefly explained. The change is going on regularly to the extent of about four minutes of time daily, amounting in a month to two hours. This monthly alteration in the position of the stars at midnight is very appreciable in the successive diagrams. As the apparent positions of the stars thus change relatively to the meridian at midnight, or indeed at any fixed hour, in the different months of the year, we have selected a day in the INTRODUCTORY AND EXPLANATORY. middle of each month for their delineation. But although the star-maps in January represent the appearance of the heavens at midnight on the 15th of that month, yet the same maps are equally applicable at other night-hours in subsequent months of the year. The same remark may be repeated for each diagram. For the convenience of those who may use them at any other hour than midnight, we have prepared the following tabular statement, which gives, at one view, the hour and month when each diagram of the series is available for comparison with the sky :— JANUARY. HILE comparing this series of diagrams with the sky, the observer is supposed to be stationed in some position where he can command an uninterrupted view of the heavens from the north to the south horizon. To do this properly, he must be out of doors. Viewing the sky from a window of a dwelling-house is very deceptive, as about thirty degrees of the sky from the zenith is completely cut off, making the apparent altitude of the stars above the horizon much greater than the reality. In our remarks, we therefore assume that the observer has selected a favourable position, and that he has furnished himself with a hand-lamp, to enable him to make his comparison of the diagrams directly with the sky. The first thing for him to do is to find the direction of the meridian approximately. In the introductory chapter it has been stated that, in the night-time, the best method of fixing this imaginary line, is to discover the position of the North Pole, indicated very nearly by the well-known isolated star of the second magnitude, Polaris. When found, a little time will be well spent in forming some acquaintance with the general appearance of that part of the sky, so that, in future observations, the eye may fall readily upon the spot without special reference to other stars. The most popular, and by far the easiest, way of finding Polaris, is to glance at the universally-known seven stars in Ursa Major, a constellation which has probably attracted the attention of most persons. There can be no difficulty in identifying this Ursa Major group, the general form of which is so well understood. Now, at midnight in January, the two stars nearest to the zenith, or point over-head, have for ages been popularly designated the Pointers, because a straight line drawn from Merak, the more southerly, to Dubhe, the more northerly of the two, will lead, if continued, very nearly to Polaris. These two leading stars therefore clearly indicate the position of the Pole of the heavens and the Pole star, which is situated in a part of the sky free from other stars of a similar magnitude. Probably there will be little chance of mistaking any other object for Polaris after reading the following lines :— "Where yonder radiant hosts adorn The northern evening sky, Seven stars, a splendid glorious train, To deck great Ursa's shaggy form, |