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little water on the reef at low tide. This is most 

 particularly noticed should the weather be calm when 

 spring tides occur. 



The height of the reef is about the level of the 

 sea, and the heads of the waves, which break on it 

 with great violence in rough weather, are forced over 

 it into the shallow basin between it and the shore. 

 By this means the shallow basin is supplied with 

 water. The principal outlet for this water is " the 

 pass" between the Islands. Through this channel a 

 strong current runs and the rougher the sea on the 

 reef, the more water enters the basin, and the 

 stronger is the outward current through " the pass. " 



This current keeps the boat channel clean, and 

 prevents a bank of coral sand from being thrown up 

 between the two seas, and unitting Gabriel and Flat 

 Islands. 



The bottom of this basin is coral rock and 

 voloanio boulders and the lime from desintegrated 

 coral and pieces of shells acts like cement to bind 

 the volcanic boulders together. Over this lies a loose 

 course of broken coral, broken shells and coral sand^ 



Coral rock crops up at different place on the 

 shore, between the mouth of the pass and where the 

 reef begins to break off the shore, near the Pigeon 

 House Eock. It is particularly noticeable at about 

 half way between these places, where it runs out into 

 the shallow basin in four rocky ledges, to about from 

 150 to 200 yards from the shore. This rock is like 

 some of the Oolitic rocks, from which are cut many of 

 the large stone filters used in Mauritius to filter water. 

 It is entirely composed of broken pieces of shells 

 and coral ; like the sand ou the shores of Mauritius 

 and other tropical Islands. Lime is the binding mat- 

 er which holds the pieces of shells and coral together. 



