MODE VI. CORAL ROCK. 4/3 



is only superficial ; at others it penetrates far into 

 the substance of the stone. The explanation of 

 the appearance is not obvious; but perhaps some 

 liquid, holding the colouring matter in solution, 

 originally insinuated itself into the clefts by which 

 the laminae are separated from each other, and 

 deposited this, particle by particle ; by something 

 like that continuous attraction, if the term is 

 allowable, which takes place in the freezing of 

 moisture on a pane of glass." * 



MODE VI. CORAL ROCK. 



The texture resembles clustered corals, or 

 madrepores, cemented by limestone j-. 



This substance has not yet been mentioned in Origin, 

 books of mineralogy, though large islands and 

 vast shoals in the South Sea, particularly on the 

 east of Australasia, are wholly composed of it, 

 according to the accounts of navigators. Coral 



* Vol. i. p. 31. See also Da Costa, p. 144, who adds, that a 

 similar slate is found near Bath. The white flag common in the 

 north of England he ranks among the alkaline calcareous sand- 

 stones : it is spangled with mica, sometimes very prettily, especially 

 that with little needles, lying in a diagonal form. 



f The characters of limestone apply to many of the rocks in this 

 domain, and are therefore not repeated. The characters are als 

 Sometimes implicated in the descriptions. 



