240 MARK S. IV. JEFFERSON 



It results from these considerations that the greatest amount 

 of stones and seaweed will be flung up on the upper beach on 

 the rise of a spring tide when a strong gale is blowing from the 

 east. The beach is not, however, a convenient place for obser- 

 vation at such a time, nor can it be visited save by observers 

 resident in the neighborhood on account of floods and washouts 

 that result and interrupt railroad and other travel. For this 

 reason it is more practicable to study what occurs during spring 

 tides with only moderate winds. 



Such an ocasion was November 7, 1896 when I was fortunate 

 enough to reach the beach shortly before high tide. The ordi- 

 nary waves were playing up and down the bays as far as the belt 

 of seaweed, BB, Fig. 2. These waves advanced with a front 

 indented by the stony points at their maximum advance. But 

 at intervals of about ten minutes a great wave broke evenly upon 

 the line of seaweed, sending tons of water over the cobblestones 

 above. The zone of seaweed in the diagram should be under- 

 stood to have a depth of 12 to 18 inches. Shoreward from the 

 crest, the weed slopes and thins. It is more or less present 

 even on the cobble belt AA. But the zone represented on the 

 diagram marks the crest. Immediately after breaking, the wave 

 outside the zone BB retires, leaving considerable masses of water 

 imprisoned behind the weed. This can only escape through 

 occasional breaks in the wall of seaweed and at these points 

 streams of considerable strength set outward. This moment is 

 recorded in Fig. 3. The wave has just broken evenly along the 

 whole line. At the instant represented by Fig. 3 the water may 

 be seen pouring toward the opening from right and left behind 

 the weed, streaming out through the break in the weed whence 

 the water is distributed fan-like in every direction. A similar 

 fan in the water to the left indicates the opening of another out- 

 let through the weed. The quantity of water flung behind the 

 weed barrier when such a great .wave breaks is sufficient to main- 

 tain a strong current through the outlet during the rise and fall 

 of several ordinary waves, which only play up and down the bays. 

 As the great wave recedes we note the stony promontories, 



