“O Sun-- Thou shin’st in boundless majesty abroad, High gleaming from afar--prime cheerer, heat; Of all material beings first and best! Efflux divine! Without thy quickening glance, our cumbrous mould Were brute, unlovely mass, inert and dead; And not as now, the sweet abode of life. How many forms of Being wait on Thee! Inhaling spirit; from the unfetter’d mind, By thee sublimed, down to the daily race, The mixing myriads of thy setting beam-- The vegetable world is also thine! The very dead Creation, from thy touch, Assumes a mimic life. But this And all the much-transported Muse can sing, Are, to thy splendour, dignity, and _use_, Unequal far! Great delegated Source Of Light and Life, and Grace and Joy below.” With reference to the vegetable kingdom, we see that the most delicate of the discous plants or flowers turn constantly towards the sun; it is also well known that the change of position of the leaves of plants, at different periods of the day, is entirely owing to the agency of light; plants growing in the shade, or in darkness, are pale, and without their natural and healthy colour--they become ‘etiolated’ or blanched. Gardeners avail themselves of a knowledge of this fact, and, by excluding the light, they obtain celery, lettuce, &c., in a white state. If a potato be placed in a dark cell, with but one small aperture for the admission of light, on germinating, the sprout will turn and grow towards the light, and will continue pale and light until it reaches the light, and becomes fairly exposed to its stimulus, when its natural and healthy colour will be assumed. Light contributes to the maturity of seeds, fruit, and flowers. Professor Davy found by experiment that red rose-trees, carefully excluded from light, produced roses almost of a white colour. Vegetables are not only indebted to the light for their colour,[3] but their taste and odour are likewise derived from, or at all events greatly influenced by, the same source. Light is also an essential element in the topographical arrangement of plants. The southern slopes of our hills and mountain ranges are always clothed with a more fully developed race of plants than the northern; this depends wholly upon the greater degree of light and heat which the former enjoy. The more free the exposure, the more readily will most plants blossom, and yield a rich fruit; so well is this understood in the grape countries on the Rhine, that the right bank of that river, which faces the sun, is reckoned to be much more valuable than the left, and commands a higher price for its wines.