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On Coral Islands and Beefs, as described hj Mr Darwin. By 



Charles Maclaren, Esq., F.R.S.E.* 

 Coral islands are one of the wonders of Natural History. 

 That masses of rock, many leagues in extent, should be founded 

 in the depths of the ocean, and built up to the height of hun- 

 dreds of feet, by minute animalculae scarcely visible to the 

 naked eye, is a phenomenon calculated to stagger the unlearned, 

 and which even philosophers were slow to believe. The struc- 

 ture and arrangement of ths mineral masses thus produced, 

 are not less singular than their origin, and present problems 

 which have puzzled and divided men of science. An excellent 

 work on the latter branch of the subject has been recently 

 published by Mr Charles Darwin, in which this able naturalist 

 has condensed and systematized his own observations and those 

 of his predecessors, and, for the first time, presented us with a 

 complete view of these singular objects. The facts have led 

 him to some new and highly curious conclusions bearing on 

 the past and future physical history of the globe. An outline 

 of these may not be without interest. 



Corals— What tliey are.— The term coral includes two objects 

 —the animal, called the Polype or Polypifer, and the tenement 

 in which it lodges, called the Polypidom, or, more usually, the 

 " Coral." The solid massive corals, which form reefs and islands, 

 are chiefly found in tropical seas, and it is of these we mean 

 to speak. 



Polypes cannot live unless constantly immersed in water, 

 or beaten by the surf: even a short exposure to the sun 

 kills them ; and hence the reefs they build terminate below 

 the surface, sometimes one or two feet, sometimes several 

 fathoms. Different species inhabit different depths. Some 

 slender branching corals are found living (that is, tenanted 

 by living animalcula?) at the depth of a thousand feet ; but 

 the massive corals which constitute reefs, do not exist at a 

 greater depth than 20 or 30 fathoms ; and there are species 

 which delight in the surf, and carry on their labours amidst 

 breakers which would swamp a boat. All the varieties included 

 in coral reefs are not known with certainty. Those found 

 near the top by Mr Darwin were the Porite and Millepore, 



* This Article is slightly abridged from the original. 

 VOL. XXXIV. NO. LXVII. — JANUARY 1843. C 



