ORIGIN OF THE CORAL LIMESTONE. )) 



went on, why does not the same thing take place 

 now ? or why did not the loose sand, which com- 

 poses the greater part of the same beach, in the 

 same position, become consolidated ? Partial 

 springs, containing- carbonate of lime, are of 

 course improbable in so small a heap of low 

 sand as the islet is composed of. Either then the 

 stratification and consolidation is the result of a gra- 

 dual deposition beneath the level of low water, in 

 which case a movement of elevation must have 

 taken place, which in so small a spot seems a diffi- 

 cult and gratuitous hypothesis ; or else the present 

 structure must have been produced in the interior 

 of a mass of loose sand by the infiltration of sea or 

 rain water, or some other cause of which we are 

 ignorant. 1 say in the interior, for had it been on 

 the outside, what was to defend it from the wash of 

 the sea that is now breaking down the hard solid 

 rock, and shifting and washing backwards and for- 

 wards the loose sand of which the present beach is 

 composed. After the interior of such a mass of 

 sand had been consolidated, the loose exterior may 

 have been washed away and the solid rock exposed. 

 The speculation concerning the structure of this 

 little island may seem a very unimportant circum- 

 stance even to the geologist ; but it is not so, as this 

 same rock is found along every beach and at every 

 island near the coral reefs of Australia, and I 

 believe in other parts of the world also. 



Jan. 13 to IS.-— The Fly, the Bramble, and the 

 boats were engaged in surveying the group of 



