When the sun rises in splendour above the eastern horizon, tinting the sky with varied colours, lighting up the clouds which till then have been but dark patches on the heavens, bringing out the colours of hill and dale, rock and river, fields and woods, the heart gladdens at the spectacle. A pleasing melancholy falls on us as the light fades away at eventide, tint after tint vanishing, until at length the gloom of night enshrouds all. The full splendour of mid-day, the chastened splendour of a moonlit night, and the glory of the heavens when "all the stars shine, and the shepherd gladdens in his heart," stir the soul in like manner; and it might seem to many that to analyse these glories, to explain their scientific meaning, would be to rob the mind of the pleasure it had before found in such scenes. Many would be disposed to think that a purer enjoyment is expressed by Augustine than any student of science could find in the wonders of light, in those words in which he expresses his sense of the loveliness of fair forms and brilliant colours. "For light, queen of the colours," he says, "bathing all I can look upon, from morning till evening, let me go where I will, will still keep gliding by me in unnumbered guises, and soothe me whilst I am busy at other things, and am thinking nothing of her." But the sensuous pleasure afforded by light is enhanced, while a purer and higher enjoyment is superadded, when the real meaning of the display is understood. As the astronomer sees in the sun a more glorious object than the sun of the poet, recognising in imagination not only the visible splendour of that orb, but the mighty energy with which it is swaying the motions of a scheme of circling worlds, the wondrous activities at work throughout its entire frame, the inconceivable tumult which must prevail in that seemingly silent globe, so the glories of light, rightly understood, are far more impressive than as they appeal simply to the senses. [Illustration: Fig. 1.--Sunrise on the Righi.]