88 LECTURE VII. 



tating, or forming at the bottom as a sediment, 

 this earthy matter, they are enabled to build up 

 the cells in which they live, and by which their 

 soft, jelly-like substance is defended. These 

 cells form what is called the coral or madrepore, 

 and the quantity of caustic lime thus removed 

 from its state of solution in sea-water, and 

 thrown down or precipitated as an insoluble 

 earth, or earth gathering a crust, may be con- 

 ceived when I tell you that islands and reefs of 

 coral, upwards of one thousand miles in extent, 

 are formed by the agency of these seemingly 

 frail and insignificant living beings. 



I have said that these insects form islands, 

 and, before I proceed further to show you the 

 object of animal life in removing the caustic lime 

 from the sea, I will tell you how this is per- 

 formed. The operations of the coral insect, 

 through a long succession of ages, proceed up- 

 wards from the original foundations, until the 

 surface of the sea is reached, when the work 

 ceases. Sea-birds settle on these rocks of coral, 

 sea-weeds are driven on them, and other sub- 

 stances, all of which, added to the manure of 

 birds, form a stratum of soil, on which seeds are 

 either dropped or washed by the tide, and thus 



