Climate and the season of the year, have a considerable influence on the colour of the sky. You know what a rich full blue is over us in the hot months of summer; and I hope you have before now enjoyed the pale blue of a clear winter's day, when the brown and bare branches of the trees have showed against it, and all the rivers and ponds have been frozen as solid as a stone pavement. When I see some of you sliding and skating on the glassy ice, at such times I am ready to wish I was a boy again, to join in your pleasures. However, I have had my turn, and old age has its pleasures as well as youth, only we are apt to get into a way of looking at all past times as happier than the present, which is both foolish and wicked. If we were to keep ourselves diligently engaged in doing our duty, we should always be happy, whether old or young. But the darkest blue sky you have ever seen in your country, is light compared with the skies of hot climates. In them you often see a deep rich indigo; at other times you are under a canopy of reddish orange, almost copper colour, like that which was called in the poem I quoted to you when describing the tropical sea, "a hot and copper sky." The elevation of the observer above the surface of the earth, is likewise another cause of variation. I have never myself ascended a mountain sufficiently high to see this, but I have been told by a gentleman who had been at the top of Mont Blanc, that the sky there looked nearly black. As you must have seen them yourselves, I need only remind you of the glorious changes of colour by the alteration of the light at the different times of day. I hope none of you are so lazy as not often to have enjoyed the rosy mornings; then there is the grey twilight of evening, and the splendours of the setting sun in the west, round which the deep orange shades off into the most delicate yellow, which again glides imperceptibly into pale blue towards the east. Then the moon, when she has the heavens all to herself, and the stars, when they are shining out boldly in her absence, each make the sky so beautiful, and are so beautiful in themselves, that one cannot exceed the other. I love to look at the moon when the winds rend the clouds asunder, and drive them tumultuously along, and you see her now and then in the dark blue depths between. But if I were to tell you all the ordinary appearances in the sky which I love, I should leave no room to describe its wonders; which will not do, because I meant this book to give you an account of things which most of you have not seen. CHAPTER II. THE AURORA BOREALIS. During the winter months in the Polar Regions, the sun never rises above the horizon; and during summer it performs in appearance a little circle round the pole of the Heavens, and never goes out of sight. You may learn in what manner this is occasioned by the position of those countries on the surface of the earth, from the book called "The Wonders of the Telescope."