THE MICROSCOPIST IN BERMUDA. 117 



this foundation they continue to build as long as they are un- 

 covered by the lowest tides. Such a profusion of life as is found 

 in the coral beds, requires a constant change and commotion in 

 the waters which supply them their building material. There- 

 fore these animals flourish best in the fiercest surf and on the 

 stormiest coasts. The most dreaded of all the sailor's perils lie 

 always concealed beneath the most tempestuous waters of the 

 ocean. 



The theory of coral islands is that there was once a much 

 larger island perhaps a mountain or a range of mountains in 

 the place where such an island now is. That the reef corals then 

 built an encircling barrier around its shores, called in this case a 

 barrier reef; and that, as gradually the island sank into the 

 ocean, the corals kept on raising and narrowing in their reefs, 

 until finally the main land entirely disappeared beneath the 

 waters, leaving only the more or less circular reef about it. As 

 any barrier, thus thrown up against the action of the waves, has 

 a tendency to accumulate, and to raise into shore lines, the sand 

 and shells of the ocean, so there is soon dry land where those 

 barrier reefs once were. There are hundreds of these circular 

 islands, called atols, in the Pacific Ocean. Some with a rem- 

 nant of the old island still in the center, others with only water, 

 into which, through a narrow opening that is usually left on the 

 leeward side, ships can sail in and find a safe anchorage. 



This is undoubtedly the condition of the circular reef about 

 the Bermudas, except that the waves and the winds have made 

 dry land on only a portion of the southern line of the reef. 

 Outside the reef the bottom declines somewhat rapidly, and in a 

 few scores of miles from it the water is almost unfathomable. 

 There are further evidences of the gradual sinking of the islands 

 during geological times, which I will not stop to enumerate. It 

 is pretty certain therefore that there w r as once a larger and very 

 different island in the region where the Bermudas now are and 

 that as it gradually sank into the waves, the reef builders kept 

 working in and up towards the surface, until finally every vestige 

 of the old island disappeared ; and there is now above the surface 

 of the ocean only the material which the waves have washed up 



