World of the Dark 



far more delicately and instantaneously than any device, attached 

 to the most perfectly constructed camera, regulates the amount 

 of light transmitted through its lens. The tiger in the jungle 

 sees what is going on about him in the starlight as well as we 

 see what is happening in the noontide. I have studied the 

 eyes of lions and tigers in the dark. The yellowish-green iris in 

 the night almost entirely disappears from viev/, and shrinks 

 down into a narrow ring. The windows of the eyes have the 

 curtains drawn back wide, so as to let in all the light which the 

 darkness holds within itself. The great orbs then look like 

 globes of crystal, framed in a narrow band of gold, lying on a 

 background of the blackest velvet, while in their pellucid depths, 

 tires, tinged with the warm glow of blood, play and coruscate. 



The eyes of many birds are adapted to the dark. This is 

 true, as everybody knows, of the owls, and of their not distant 

 relatives, the goat-suckers. I remember having, when a boy, 

 dissected an owl, which I found dead after a long protracted 

 period of intensely cold weather. The thermometer had stood 

 at twenty degrees below zero for several nights in succession. 

 The earth was wrapped deep in snow. Upon the sleety crust 

 I found a great horned owl, lying dead, and frozen stiff. It may 

 have died of old age, or it may have starved to death. The 

 instinct of the child, who takes his toys to pieces in order to see 

 how they are made, seized me, and, with a sharp penknife as a 

 scalpel, and a few needles set in sticks of pine, I took my owl 

 apart, and made drawings of what I found. I did not then 

 know the names and functions of all the parts, but the drawing 

 of the eye, which I made, I still have in an old portfolio, and 

 there I saw it the other day. The eye of an owl is a wonderful 

 piece of mechanism. It is a wide-angle lens of beautiful powers 

 of adjustment. It is adapted to taking in all the light there is, 

 when the light is almost all gone; and it is so contrived as to 

 shut out light, when too much of its splendor would dazzle 

 and hurt. 



Among the insects thousands and tens of thousands of 

 species are nocturnal. This is true of the great majority of the 

 moths. When the hour of dusk approaches stand by a bed 

 of evening primroses, and, as their great yellow blossoms 

 suddenly open, watch the hawkmoths coming as swiftly as 



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