LIGHT AND LIFE. 307 



Not only the color of organized beings, but their shape too, is 

 linked with the action of light, or rather of climate. The flora of the 

 globe gain increasing perfection as we go from the poles toward the 

 equator. The nearer these beings approach the highest degree of heat 

 and light, the more lavishly are richness, splendor, and beauty, be- 

 stowed on them. The energy and glory of life, perfect forms as well 

 as brilliant arraying, are the distinguishing mark of the various and 

 manifold races in tropical regions, giving this privileged world its 

 characteristic aspect. A pure emanation from the sun, Nature here 

 lives wild and splendid, gazing unshrinkingly, like the Alpine eagle, on 

 the eternal and sublime source which inundates it with heat and glow. 

 Look, now, at the regions of the pole ! A few dwarfish shrubs, a few 

 stunted and herbaceous plants, compose all its flora. Its animals have 

 a pale covering and downy feathers ; its insects, sombre tints. All 

 around them are the utmost limits of life ice invades every thing, the 

 sea alone still breeds a few acalephs, some zoophytes, and other low 

 rudimentary organizations. The sun comes aslant and seldom. At 

 the equator he darts his fires, and gives himself without stint to the 

 happy Eden of his predilection. 



IV. 



It remains to note the relations of light to that being most sensitive 

 to its influence, and best able to express its effects, man himself. The 

 new-born child seeks the day by instinct, and turns to the side whence 

 light comes, and, if this spontaneous movement of the infant's eyes is 

 thwarted, strabismus may be the consequence. 



Of all our organs the eye is the one that light especially affects. 

 Through the eyes come all direct notions of the outer world, and all 

 impressions of an aesthetic kind. Now, the excitability of the retina 

 shows variations of every kind. Prisoners confined in dark cells have 

 been known to acquire the power of seeing distinctly in them, while 

 their eyes also become sensitive to the slightest changes in the inten- 

 sity of light. In 1766 Lavoisier, in studying certain questions upon 

 the lighting of Paris, which had been given for competition by the 

 Academy of Sciences, found after several attempts that his sight wanted 

 the necessary sensitiveness for observing the relative intensities of the 

 different flames he wished to compare. He had a room hung with 

 black, and shut himself up in it for six weeks in utter darkness. At 

 the end of that time his sensitiveness of sight was such that he could 

 distinguish the faintest differences. It is very dangerous, too, to pass 

 suddenly from a dark place into a strong flood of light. The tyrant 

 Dionysius had a building made with bright, whitewashed walls, and 

 would order wretches, after long seclusion from light, to be suddenly 

 brought into it. The contrast struck them blind. Xenophon relates 

 that many Greek soldiers lost their sight from reflections off the snow 

 in crossing the mountains of Armenia. All travellers who have visited 



