great body of earth which forms its bottom. It is at the bottom of 

 the sea that the greatest wonders are performed, and the most rapid 

 changes are produced ; it is there that the motion of the tides and 

 the currents have their full force, and agitate the substances of 

 which their bed is composed. But all these are almost wholly hid 

 from human curiosity ; the miracles of the deep are performed in 

 secret; and we have but. little information from its abysses, except 

 what we receive by inspection at very shallow depths, or by the 

 plummet^ or from divers, who are known to descend from twenty 

 to thirty fathoms. 



\_PhiL Trans. Bujfon. AblcFortis. Ncizton. Goldsmith. 

 Payne.] 



SECTION 111. 



Formation of Coral Islands. 



FEW things are more curious or difficult to explain than the pro- 

 cligious quantity of coral formed in the sea, especially in the tropical 

 regions. Coral is the produce of different species of verines, or \\ orm 

 tribes, and it consists chiefly of carbonate of lime. Now it is difficult 

 to conceive where these animals procure such prodigious quantities 

 of this substance. Sea-water, indeed, contains traces of sulphat of 

 lime, but no other calcareous salt, as far as we know. Hence it 

 \vould appear, that these creatures must either decompose sulphate 

 of lime, though the quantity of that salt contained in sea-water 

 seems inadequate to supply their wants, or, they must form carbonate 

 of lime from the constituents of sea-water, in a way totally above 

 our comprehension. Be that as it may, there is one consequence of 

 this copious formation of coral in the tropical regions of consider, 

 able importance to navigation, which has been clearly pointed out 

 by Mr. Da) rv in pie, and is now pretty well understood. 



There is not a part of natural history, remarks this accurate 

 observer, more curious, or perhaps to a navigator more ureful, 

 than an enquiry into the formation of islands. The origin of 

 islands in general, is not the point to be discussed, but of low, 

 flat, islands in the wide ocean, such as are most of those hi. 

 tUcrto discovered in the vast South. sea. These islands are ge- 



