As for us who have the happiness of possessing the sense of sight, we know this mysterious agent more by the enjoyment that we have derived from it, than from any analysis we have made of its nature. It is an endless chain that connects us with the entire universe; a bond that laughs at distance and spans the abysses of space. By means of light we can appreciate the beauties of hue and form, and by its power we touch as it were the inaccessible. It constitutes the most intimate connexion between ourselves and external objects—a connexion that seems even to alter our temper, disposition, and character, according to the variations of its intensity. The dull and foggy days of winter, those days when sleet and rain struggle in the atmosphere, spread like a veil over us, and throw a shadow upon our life. The return of the bright spring sun, the reappearance of light and blue sky, on the contrary, open up our hearts and minds, gay nature enchants us once more, and a feeling of fresh happiness prepares us for the coming glories of the newly risen year. This intimate connexion between the light of heaven and the human mind, hallowed as it is by our desire to rise towards the Source of all light, might be made the subject of many eloquent pages; and it would be an interesting and useful task to show the gradual progress of mankind from those ancient people who trembled at the approach of darkness, and who fervently saluted the dawn with prayers and praises, down to the philosophers of the present age, who investigate its effects with so much reverential joy. But we must cease paying any more attention to the superficial action of this marvellous force which in these latter days has become, in the hands of man, the source of so many illusions and the origin of a complete world of rich and brilliant pictures, but which after all only exist in the imagination. It was believed for a long time that light was a compact mass of tiny particles emitted by luminous bodies, which struck our eyes and so produced the phenomenon of vision. These particles or molecules were naturally thought to be extremely minute, and the objects illuminated by them were supposed to throw them off as if they were endowed with elasticity. Under this hypothesis, light was a material body. The illustrious Newton was the first propagator of this theory; the last was M. Biot, a French philosopher, lately dead.