50 
NATURE FOR ITS OWN SAKE 
Sky lines 
teen at seu. 
the horizon-ring appear so small, as upon the 
opensea. The ship upon which we stand is the 
centre of a watery field, the mainmast points 
overhead to the centre of the blue firmament, and 
all around spreads the deep azure glow. Judging 
from vision alone the world appears very small. 
The uttermost rim is just beyond us. The ex- 
panse of the sea and the reach of the atmos- 
phere about the whole globe are practically un- 
felt. Even the height overhead seems greater 
than the sweep before and after us. The limi- 
tation becomes still more limited when the va- 
pors lying along the surface of the sea thicken 
the air and obscure the sight. We cannot as a 
general rule under favorable conditions see more 
than fifteen or twenty miles across sea water, 
and even in calm weather the horizon is often 
clouded by vapor banks that lie along it like a 
row of faintly seen hills. All this helps the illu- 
sion of being circled and shut in by the horizon. 
Then again the sense of distance by perspective 
lines is practically annihilated. Occasionally 
the skeleton masts and black trailing smoke of 
an ocean steamer, or the tower-like looking 
sails of a square rigged ship appear, and act as 
catch-points ; but these are slight, and as for 
aérial distance we recognize it only by obscurity 
