120 



NATURE FOE ITS OWN SAKE 



and such thicknesses are infrequent, if, indeed, 

 not impossible. 



The lines of a wave made by light-and-shade 

 and the variation of color are somewhat de- 

 pendent upon wave motion. The swell of 

 the Southern seas has about the same lines as 

 the smaller rolls of a Dakota prairie. The 

 horizontal ridge and its corresponding valley 

 are distinctly marked, light-and-shade and color 

 play all along them, and the heavens above 

 are rolled and unrolled from them in long, 

 flashing reflections. As soon as the sur- 

 face is broken by wind the lines are blurred, 

 and the reflection is lost in local hue, though 

 each little wave continues to throw off from 

 itself the tiny reflection of light and color, like 

 a portion of a broken mirror. The general 

 form and heave of the wave are not lost ; its 

 surface only is changed. The waves on the 

 North Atlantic are quite different from this 

 tropical undulation. They are shorter, sharper, 

 more ragged in surface, and they have a cross- 

 blow tumble and toss about them that some- 

 times defy the line and make only flashing 

 light and color possible. In heavy and steady 

 winds they heap up in enormous ridges, follow- 

 ing each other, file upon file, like other waves, 



