I have already spoken about the seeming motions of the stars as a whole, once believed to be real, and now known to be only caused by the motions of our earth. For just as the turning of the earth upon her axis makes the sun seem to rise every morning in the east, and to set every evening in the west, so that same continued turning makes the stars seem to rise every evening in the east and to set every morning in the west. When we speak of the stars as rising in the east, we do not mean that they all rise at one point in the east, but that all rise, more or less, in an easterly direction--northeast, east, and southeast. So also with respect to the west. It is to the east and west of the earth as a whole that they rise and set--not merely to the east and west of that particular spot on earth where one man may be standing. All night long fresh stars are rising, and others are setting, and if it were not for the veil of light made by the sunshine in our atmosphere, we should see the same going on all day long as well. There are some constellations, or groups of stars, always visible at night in our northern hemisphere; and there are some constellations never visible to us, but only seen by people living in the southern hemisphere--in Australia, for instance. There are other constellations which appear in summer and disappear in winter, or which appear in winter and disappear in summer. This change is caused by our earth’s journey round the sun. It is not that the constellations have altered their place in the heavens with respect to the other constellations, it is merely that the earth has so altered its position in the heavens that the groups of stars which a short time ago were above the horizon with the sun by day are now above the horizon without him by night. Mention has been a good many times made of the axis of the earth ending in the North and South Poles. If this axis were carried straight onward through space, a long, slender pole passing upwards into the sky without any bend, from the North Pole in one direction and from the South Pole in the other,--this would be the pole of the heavens. The places of the stars in the sky are counted as “so many degrees” from the North and South Celestial Poles, just as the places of towns on earth are counted as “so many degrees” from the North and South Poles of earth. There are atlases of the sky made as well as atlases of the earth. The constellation of the Great Bear is known to all who have ever used their eyes at all to watch the heavens. Almost equally well known are the two bright stars in this constellation named the Pointers, because, taken together, they point in nearly a straight line to a certain important star in the end of the Little Bear’s tail, not very distant.