NATURE FOR ITS OWN SAKE 
CHAPTER I 
PURE AND REFLECTED LIGHT 
A FISH at home under some ledge of rock in 
the depths of the sea, what does it know of sun- 
light ? Doubtless the pupils of its eyes con- 
tract and expand with the lights and shadows 
that break across the hills and valleys of the 
ocean world, but how dim must be those lights, 
how densely dark those shadows! A ray of sun- 
shine passing through five hundred feet of wa- 
ter is broken, deflected, almost extinguished ; 
and the eyes that look upward toward the ight 
through that great green lens of wave can 
gather but a faint glimmer of the truth. They 
are focused for the ocean depths, and when the 
fish is brought up to the open day the eyes are 
instantly set, and stare without meaning. The 
first flashing sunbeam doubtless shocks them 
senseless. The truth when revealed is blinding, 
and our sunlight is final truth to the fish. 
Knowledge 
of light, 
