Bright effluence of bright essence increate,—
Thy fountain who shall tell? Before the sun—
Before the heavens thou wert, and at the voice
Of God, as with a mantle, didst invest
The rising world of waters dark and deep.”
Commencing with the properties of light, we find its influence on inorganic bodies and vegetables to be unequivocal; in short, it may be said that so very extensive is its influence, that there is not a substance which, when exposed to its action, does not experience some alteration. Without light, independently of the heat which is its ordinary concomitant, there would scarcely exist a trace of vegetation, and when we reflect on the remarkable dependence of the animal and vegetable kingdoms on each other, the animal by the extrication of carbonic acid gas, affording a fluid essential to vegetation; the plant, on the other hand, by the emission of oxygen, supplying the atmosphere with the gas which is equally necessary for the well-being of the former, we cannot suppose light to be less essential to animal life.
The chemical effects of light, and its influence on animal and vegetable vitality, have much engaged the attention of philosophers:—
“O Sun—
Thou shin’st in boundless majesty abroad,
High gleaming from afar—prime cheerer, heat;