FRINGING REEFS. 115 



Fringing reefs are formed of exactly the same genera of corals as 

 the barrier reefs and atolls. The reef may be from 250 to 500 

 yards wide. The most common corals forming the reefs belong to the 

 genera Porites, Millipora, Pocillipora, and the brainstone coral Mean- 

 drina. 



Fringing reefs are met with at both ends of the Red Sea, 

 on both the Arabian and African shores. They extend all down 

 the Zanzibar coast and the coast of Mozambique. They surround 

 the Seychelle Islands and the Mauritius, and occur round the north- 

 east and south-west shores of Madagascar. They occur on the 

 steeper shores of Ceylon, and round the Nicobar Islands, and are 

 prolonged on the southern coast of Sumatra, and occur along the 

 whole of the chain of volcanic islands which ends with Timor. 

 Fringing reefs occur between Borneo and Malacca, around the 

 Loochoo Islands, among the Philippines, southward to Ceram. The 

 Mariana Isles have fringing reefs, as have the Solomon Isles, the New 

 Hebrides, the Friendly and Navigator Isles; and the Sandwich 

 Islands are thus margined. Fringing reefs also more or less surround 

 nearly the whole of the West Indian Islands, and form a southern 

 prolongation of Florida. Coral reefs are, however, entirely absent 

 from the Pacific Coast of America, and are rare on the coast 

 of Asia, east of the Persian Gulf. Thus it will be seen that with the 

 exception of the reefs on the African coast, they almost all occur 

 around islands, and especially on eastern coasts of the great masses of 

 land. The fringing reefs appear usually to grow on shores which are 

 either stationary, or which in comparatively recent times have been 

 upheaved. Thus in Florida, reefs are found extending inland, exactly 

 similar to those which are now forming on the shores ; and from these 

 the late Louis Agassiz 1 endeavoured to estimate the period during 

 which the reefs must have been growing from the known rate of in- 

 crease of the corals on the Florida coast. He considered the existence 

 of these inland reefs to represent duration of time, equivalent to many 

 millions of years. But the rate at which corals increase varies with 

 the species and in different seas. 



In the Red Sea, where the temperature is extremely high, 

 never falling below 70, and often rising to 120, the coral grows 

 so slowly, that its rate of increase is almost imperceptible. On 

 the coast of the United States and in other places corals have been 

 taken up from year to year, and measured and been found on an 

 average to grow about half an inch in twelve months. But in one 

 case where coral has grown upon the sunken British ship the 

 " Shannon," it was found that supposing the coral to have commenced 

 growing as soon as the ship reached the bottom, it could not have 

 increased at a slower rate than three inches in a year. This coral 

 belonged to one of the more open branching types of the genus 

 Madripora. In other cases corals were planted on the coast of Mada- 

 gascar, which in six months appear to have reached a height of nearly 

 three feet; and it is recorded that a ship which had been in the 

 1 Agassiz, Natural History Studies. 



