The third constituent of the sunbeam is actinism—its property being to produce chemical effects. So long ago as 1556, it was noticed by those strange seekers after impossibilities, the alchemists, that horn silver, exposed to the sunbeam, was blackened by it. This phenomenon contained the germ of those most interesting discoveries which have distinguished the present age; but, in their ardent search for the philosopher's stone and the elixir of life, they overlooked many an effect of their labors which might have led them to important truths.
As yet, the effects of actinism have been more studied in the inanimate than the organic creation. Still, in the vegetable kingdom, its power is known to be of the utmost importance. A seed exposed to the entire sunbeam will not germinate; but bury it in the earth, at a depth sufficient to exclude the light, yet enough to admit actinism, which, like heat, penetrates the earth to some distance, and soon a chemical change will take place; the starch contained in the seed is converted into gum and water, forming the nutriment of the young plant; the tiny root plunges downward, the slender stem rises to the light, the first leaves, or cotyledons, then unfold, and now fully expand to the light, and a series of chemical changes of a totally different nature commence, which we have before noticed, when speaking of light. Experiments clearly prove that this change is to be attributed to actinism, and not to heat. Glass has been interposed of a dark blue color, which is transparent to actinism, though opaque to light and heat, and germination has been thereby quickened. Gardeners have long known this fact practically, and are accustomed to raise their cuttings under blue shades. There is no doubt that actinism exercises a powerful and beneficent influence on plants during their whole existence, but science has yet to demonstrate its nature; and it is curious to observe that the actinic element is most abundant in the sunbeam in the spring, when its presence is most essential in promoting germination—in summer the luminous rays are in excess, when they are most needed for the formation of woody fibre—and in autumn the heat-rays prevail, and ripen the golden grain and the delicious fruit; in each day the proportions of the different rays vary—in the morning the actinic principle abounds most, at noon the light, and at eventide the heat.
The influence of actinism on the animal world is not well known; but it is probable that many of the effects hitherto referred to light are in reality due to actinism. It has the strange power of darkening the human skin, causing the deep color of those tribes who inhabit the sunniest regions of the earth; and even in our own country, in summer, that darkening of the skin called sun-burning. Doubtless, more careful investigation will discover this principle to be equally important to the life and health of animals as either of its closely allied powers of light and heat.
Our knowledge of actinic influence on inanimate nature is not so scanty, for it is now a well established fact, that the sunbeam can not fall on any body, whether simple or compound, without producing on its surface a chemical and molecular change. The immovable rocks which bound our shores, the mountain which rears its lofty head above the clouds, the magnificent cathedral, the very triumph of art, and the beautiful statue in bronze or marble, are all acted on destructively by the sunbeam, and would soon perish beneath its irresistible energy, but for the beautiful provision made for their restoration during the darkness of night—the repose of darkness being no less essential to inorganic, than it is to animated nature. During its silent hours, the chemical and molecular changes are all undone, and the destruction of the day repaired, we know not how.
The art of painting by the sunbeam has been rather unfortunately called photography, which means light-painting, for the process is not due to light, but is rather interfered with by it; and, contrary to all preconceived ideas, the pictures taken in our comparatively sombre country, are more easily and brilliantly produced than in brighter and more sunny lands—so much so, that a gentleman, who took the requisite materials to Mexico, in order to take views of its principal buildings, met with failure after failure, and it was not until the darker days of the rainy season that he met with any measure of success.
THE RECORD OF A MADNESS WHICH WAS NOT INSANITY.
A fresh, bright dawn, the loveliest hour of an English summer, was rousing the slumbering life in woods and fields, and painting the heavens and the earth in the gorgeous hues of the sunrise.
Beautiful it was to see the first blush of day mantling over the distant hills, tinging them with a faint crimson, and the first smile shooting, in one bright beam through the sky, while it lit up the fair face of nature with a sparkling light. Lilias Randolph stood on the flight of steps which led from the Abbey to the park, and looked down on the joyous scene. She seemed herself a very type of the morning, with her sunny eyes, and her golden hair; and her gaze wandered glad and free over the spreading landscape, while her thoughts roamed far away in regions yet more bright—even the sunlit fields of fancy.
It was the day and the hour when she was to go and meet Richard Sydney, in order to have, at length, a full revelation of his mysterious connection with her cousin. She knew that it was an interview of solemn import to both of those, in whom she felt so deep an interest; yet, so entirely were one thought and one feeling alone gaining empire over her spirit that, even then, in that momentous hour, they had no share in the visions with which her heart was busy.