628 THE WONDERS OF GEOLOGY. Lect. VI. 



that were the whole specimen filled up and surrounded by 

 detritus, as it shortly would be at the bottom of the sea, 

 a solid block would be formed, exhibiting, when broken, 

 the remains of the Flustra, impacted in a conglomerate of 

 sand, shells, and corals. Thus we perceive that even the 

 delicate, friable, skeletons of the Flustrae of our shores, may 

 become the nucleus of a solid rock; and in the process 

 described, we have, as it were in miniature, the formation 

 of a coral reef. 



28. Coral reef of Loo Choo. — But it is in tropical 

 seas that the Meandrina, Astrcece, Caryophyllice, and other 

 stony corals, form those immense masses, which not only 

 give rise to groups of islands in the bosom of the ocean, 

 but are gradually forming tracts of such extent, that a new 

 continent may spring up where the fabled Atalantis is 

 supposed to have once flourished. From the many inte- 

 resting descriptions of the nature and formation of Coral 

 reefs and Islands, that have been published by our voyagers, 

 I select the following graphic account, by Captain Basil 

 Hall, of a coral reef near the great island of Loo Choo : — 



" When the tide has left the rock for some time dry, it appears to 

 be a compact mass, exceedingly hard and rugged : but as the water 

 rises, and the waves begin to wash over it, the polypes protrude 

 themselves from holes which were before invisible. These animals 

 are of a great variety of shapes and sizes, and in such prodigious 

 numbers, that in a short time the whole surface of the rock appears to 

 be alive and in motion. The most common form is that of a star, 

 with arms, or tentacula, which are moved about with a rapid motion 

 in all directions, probably to catch food. Others are so sluggish that 

 they may be mistaken for pieces of the rock, and are generally of a 

 dark colour. When the coral is broken above high-water mark, it is 

 a solid, hard stone ; but if any part of it be detached at a spot where 

 the tide reaches every day, it is found to be full of polypes of different 

 lengths and colours ; some being as fine as a thread, of a bright yellow, 

 and sometimes of a blue colour. The growth of coral appears to cease 

 when no longer exposed to the washing of the sea. Thus a reef rises 

 in the form of a cauliflower, till the top has gained the level of the 



