88 How Sammy Went to Coral-Land 
Shore-Reefs. There are also Barrier- 
Reefs, usually enclosing an island in the 
deep sea, and Lagoon Islands or Atolls, 
which enclose a lagoon, or lake, such as 
the one where Sammy now was. 
Near the centre of this Lagoon arose 
another ring of coral-reef, like a small 
circle within a larger circle, and in the 
centre of the second little lake so 
formed, was a tiny coral-island, dotted 
here and there with gay flowers, and 
waving palm-trees. 
Outside the reefs the white-topped 
breakers thundered on unceasingly, hut 
the calm waters of the Lagoon were undis¬ 
turbed by their fury. Far above and be¬ 
low towered the magnificent rocks, form¬ 
ing so complete a barricade that sharks 
and very large fish found it difficult to 
gain an entrance to the Lagoon, and could 
never penetrate to the inner lake, where 
