With reference to Light, its wonders, and the curious but imperfect theories respecting it, we have little to add, except with regard to its physiological action upon the eyes of man and of animals, which will be given in another place. But of its sister, Darkness--for it would not do now to call darkness the antagonist of light, since it will be seen that they work harmoniously for good--we have to say, that recent discoveries indicate that darkness is as necessary to the health of nature as light. Not only is it necessary to compose man and animals to sleep, to give rest to the over-wrought nerves of the industrious--but light is the quickening power of vegetation, and although plants grow by night, they grow, as man does, when stretched upon his bed--but some of their functions, which are actively excited in the presence of light, are at rest in darkness. Nor is this all: there is not an atom upon the face of the earth which is not affected by the rays of the sun, their light, their heat, their actinism. Colours change: some are bleached, others are darkened. All bodies are expanded. The hardest rock sustains _an effect_ from the sun's rays; and an unceasing sun, shining upon the hardest granite, would in time produce such a disturbance of its atomic condition, that adamant would crumble away to dust. The going down of the sun, therefore, marks the period when not only does the bird fly to her resting-place, and man turn to his couch; but when _every atom of a vast hemisphere_ subsides into a state of quietude, and when homogeneous particles of matter return to their mutual rest. In a few succeeding lessons, we intend to point out some of the scientific truths that are _illustrated in the use of toys_. We think we shall be able to show to our young readers, that even the hours of play may be made the periods of delightful instruction; and that there is _no_ "reason why" the acquirement of knowledge should not sweetly accord with the occasional pursuit of those pastimes by which health of body and vigour of mind are induced. But before we commence the discharge of that pleasant duty, let us say a few words respecting Carbon, that important agent in the world's history. It is, doubtless, perplexing to the minds of many persons, to understand how the _diamond_ can be _pure carbon_; how _charcoal_ can be _carbon_ a _little less pure_ than the diamond; and how _coal_ and _sugar_ can also be carbon, _less pure_ than the charcoal. The statement that in the diamond carbon exists in a different atomic condition, is almost as instructive to the inquiring mind, as to say, "It is so, _because it is_."