Masterpieces of Science 



wave, or pulsation, is propagated, but the mass 

 of the water at any given spot remains stationary, 

 except in so far as it vibrates up and down. The 

 mechanical force of the wind, however, urges the 

 surface-water forward to a small extent. A 

 fresh breeze tears off the water from the crest of 

 a wave, and scatters it as spray, and a heavy gale 

 converts this into blinding showers of salt rain. 

 The wind too catches the top of the wave, and 

 causing it to move faster than the water below, 

 urges it to leeward in the form of a graceful curl, 

 the edge of which breaks into foam. On reach- 

 ing a shore, the retardation of the deeper part of 

 the wave by friction against the sea bottom, in- 

 creases the relative velocity of the superficial 

 part, and the latter rolls over; the water bursts 

 with great force upon the land, and then sweeps 

 back as a powerful "undertow, " to the sea. 



However agitated the surface of the sea may 

 be, there is reason to believe that the disturbance 

 never extends far downwards. The more vio- 

 lent the wind, the greater of course will be the 

 agitation which it is capable of producing; but, 

 even during a storm, the waves never attain 

 to anything like the height which is often popu- 

 larly ascribed to them. It is not uncommon to 

 hear of the sea running "mountains high;" yet, 

 in a strong gale in the open ocean the height of a 

 wave, from crest to trough, rarely exceeds forty 

 feet. In the shallow seas around our own islands, 

 they are far from attaining to such a magnitude; 

 the largest waves, even in a storm, not exceeding 

 160 



