MINERALOGICAL CHANGES OBSERVED IN CORES OF FUNAFUTI BORINGS. 415 



fibrous encrusting deposit is partly composed of calcite, but by far the greater propor- 

 tion of this material is of dolomite throughout. From about 1100 feet downwards 

 the rocks show somewhat marked signs of solution. 



The lowest core of the boring is composed of consolidated dolomitised " coral-reef 

 sand." It is made up of various small organisms, or fragments of organisms, which 

 are bound together by well-marked fibrous encrusting material, which more than 

 usually resembles that occurring near the top of the boring, in that it comes into 

 actual contact with the original bodies of the rock, and is not separated from them by 

 an intervening layer of dolomite crystals. 



