42 SEA AND LAND 



to the spherical form, and of g'rcat size ; they are sometimes 

 two or tliree feet in chameter. We can, in times of heavy 

 storm, see that the surges roll these masses over and against 

 each other, and we note their constant wearing as they jour- 

 ney onward, not only in the sound of their clashing, but also 

 in the steady diminution in their size as they go farther away 

 from their place of origin. Near the points of the crescent 

 shore these rolling stones are more exposed to the action of 

 the waves than they are as they slowly creep down into the 

 curved bay, so that, notwithstanding their weight, they are 

 o-round against each other and consequently diminished in 

 bulk. As we follow them toward the centre of the crescent, 

 we observe that they constantly become smaller, until, a mile 

 or two away from the point where they escape from the cliff 

 section, they may be no larger than billiard-balls. If the 

 beach be very extended, the central portion of its front may 

 be composed of fine sand, the pebbles having been ground 

 to dust in the powerful attrition of the waves. We thus 

 arrive at the first and most important point in the history of 

 these pocket-beaches, and see that they are mills which serve 

 to grind up the rocky matter torn from the cliffs, and that 

 they bring it to the finely divided state in which it can easily 

 be taken by the marine currents to great distances. We 

 must now proceed to see the details of this admirable mechan- 

 ism of the rock-grinding mill. 



When the ocean is in its ordinary summer state of still- 

 ness, with only the light pulsation which sends a few times a 

 minute a little breaker against the beach, we find that only 

 the sand and smaller pebbles are stirred by the motion of the 

 water; but now and then, even in this peaceful time of the 

 year, storms send in more powerful surges. These may come 



