148 



THE OPAL SEA 



Spouting 

 horns. 



sins and pot holes. In addition to stone weap- 

 ons every swash of the wave may drive a long 

 tongue of water up an open vein in the rock- 

 strata of the shore until, after years of churn- 

 ing, a hole is worn through at the far end and 

 a souffieur or " spouting horn " flings a line of 

 white spray high into the sunlight with every 

 pulsation of the surf. Once the passage is worn 

 through it begins to widen. Eventually it may 

 cut off that portion of the shore, and thus by 

 isolating it, compass its fall more speedily. 



Beneath the sea at the cliff's base where there 

 is the constant pound of bowlders, sometimes a 

 smooth circle in the rock is worn. In this circle 

 gravel and stones are flung around with a 

 swing like pebbles in a glacier pot. And with 

 a similar erosive effect. It may take centuries 

 of this grinding and working under the water 

 to produce a marked effect ; but eventually there 

 is a grotto formed, and at low tide the entrance 

 is perhaps apparent. In and out tnrough this 

 entrance the waves keep dashing, further and 

 further the grotto keeps receding as the fissures 

 in the rock strata are pried open, deepened, 

 widened into galleries. The softer portions of 

 the rock crumble away, the harder portions at 

 the sides remain intact, the unwashed portions 

 at the top make a vaulted roof; and the deep- 



Rock grot- 

 toes. 



