The production of artificial light by electrical and chemical agencies will necessarily find some consideration under their respective heads. There are numerous phenomena which connect themselves with luminous power, or appear to do so, which, in the present state of our knowledge, cannot come immediately under our attention. We are compelled to reserve our limited space for those branches of science which we are enabled to connect with the great natural operations constantly going on around us. Many of these more abstruse results will, however, receive some incidental notice when we come to examine the operation of the combined physical forces on matter.
We see in light a principle which, if it has not its source in the sun, is certainly dependent upon that luminary for its manifestations and powers. From that “fountain of light” we find this principle travelling to us at a speed which almost approaches the quickness of thought itself; yet by the refinements of science we have been enabled to measure its velocity with the utmost accuracy. The immortal poet of our own land and language, in his creations of Ariel, that “tricksy spirit,” who could creep like music upon the waters, and of the fantastic Puck, who could girdle the earth in thirty minutes, appears to have approached to the highest point to which mere imagination could carry the human mind as to the powers of things ethereal. Science has, since then, shown to man that this “spirit, fine spirit,” was a laggard in his tasks, and a gross piece of matter, when compared with the subtile essences which man, like a nobler Prospero, has now subdued to do him service.
Light is necessary to life; the world was a dead chaos before its creation, and mute disorder would again be the consequence of its annihilation. Every charm which spreads itself over this rolling globe is directly dependent upon luminous power. Colours, and probably, forms, are the result of light; certainly the consequence of solar radiations. We know much of the mysterious influences of this great agent, but we know nothing of the principle itself. The solar beam has been tortured through prismatic glasses and natural crystals; every chemical agent has been tried upon it, every electrical force in the most excited state brought to bear upon its operations, with a view to the discovery of the most refined of earthly agencies; but it has passed through every trial without revealing its secrets, and even the effects which it produces in its path are unexplained problems, still to tax the intellect of man.