C8 NATURE STUDY IX SCHOOLS. 



Now I will try to explain how the Bahama Islands were formed. 

 Years ago in the glacial period, the Mississippi was ten times as wide as 

 it now is. If there were ten times as much water coming to the mouth 

 then, there must necessarily have been ten times as much mud. Now 

 the mud settles at the mouth and forms a delta ; then it flowed too fast 

 to drop the mud at the mouth. The Gulf Stream, which then flowed 

 through the Straits of Florida and straight across the Atlantic Ocean, took 

 it up and carried it to the Straits of Florida. Here the Gulf Stream 

 broadened and the mud was dropped. When the embankment of rock, 

 mud and debris was within one hundred and fifty feet of the surface, the 

 coral polyps began to build on it, and in time the Bahamas were formed. 



Florida was not there at all many years before the formation of the 

 Bahamas. There was a volcanic mountain near Florida underneath the 

 water. This mountain had an eruption and threw up earth, part of where 

 Florida is. After this eruption the water was no deeper than one hundred 

 and fifty feet, so the little coral polyps built on it. Florida is partly a 

 volcanic and partly a coral peninsula. 



< ' ,, • So the little coral workers, 



By their slow but constant motion, 



Have built up pretty islands 



In the distant dark-blue ccean ; 



And the noblest undertakings 



Man's wisdom hath conceived, 

 By oft repeated efforts 



Have been patiently achieved." 



The water inside the lagoon is calm and quiet, so that the more del- 

 icate and pretty species of coral gTOW on the innerside of the atoll, or 

 next to the lagoon. These kinds of coral are branching, forking, rose, and 

 tooth coral. The coral on the outside of the reef is more compact and 

 strong, as it has to stand the strong ocean waves. These species are the 

 head, plate, and brain coral. The Bahamas are formed mostly of head, 

 plate, and fan coral. 



The little coral animals keep on building until there are several little 

 atolls and lagoons inside the large one, and as the polyps keep on build- 

 ing, the lagoon in time fills up, and it becomes a solid coral island with 

 a few lakes and ponds. 



There are other kinds of reefs beside atolls. One is the barrier reef. 

 Barrier reefs are formed where the shore slopes suddenly and steeply down 



