wo 
NATURE FOR ITS OWN SAKE 
Atmospher- 
ic obstruc- 
tions. 
Particles in 
the air. 
We have, perhaps, a contempt for the knowl- 
edge of ght possessed by the inhabitants of 
the deep, but our contempt is somewhat shal- 
low. For we ourselves are living at the bottom 
of an even greater sea—the vast atmospheric 
ocean. We are looking up to the hght through 
countless strata of air that break and twist and 
shatter the sunbeam—looking up not through 
five hundred feet, but probably five hundred 
miles of air-wave. Perhaps, were we brought up 
and out of our sea and into the regions of space, 
our eyes, too, might be blinded by the sharp shaft 
of a pure and clear sunlight. Our knowledge of 
it is only comparative, a step upward from that 
of the fish. The truth in the superlative de- 
gree will never be attained. Human eyes have 
never seen pure sunlight, and that white light 
which we regard as such is anything but pure. 
It is not the sum of all radiation, as we are ac- 
customed to think, but the residue, that which 
remains after the passage through atmosphere. 
The air we breathe is filled with countless 
particles of dust, smoke, soot, salt crystals, 
vapor ; and these particles break light into 
color by obstructing the beams. The sun ray 
is thus disintegrated as soon as it encounters 
our outeratmosphere. Some of it is practically 
