J. S. Gardiner — Origin of Coral Reefs. 



213 



the original charts and my lack of time, means and experience 

 for a thorough survey. Yet, the fact that the great bnlk of 

 the evidence points in precisely the same direction lends con- 

 siderable support to the views put forward above, "whicli I 

 have attempted to graphically represent in the annexed figure. 



O 20 40 60 80 rOO 



IME 



Fig-. 1. — Diagram showing some points in tlae formation of the Maldives. 

 The figure represents a supposed section through the rim of one of the atolls 

 (scale in fathoms). 



A. Basis of primitive rock, cut down by the action of the currents, etc. 



B. Upgrowth of a shoal by means of deep-sea corals assisted by other 

 organisms. The more densely shaded area between B and D shows the depth 

 at which the deep corals cease to grow and the reef forms commence. The 

 reef, however, in this part is mainly formed by the medium depth corals 

 and other organisms. 



C. Outward extension of the reef by means of detritus, swept off the reef 

 above by the currents. 



D. Surface reef, formed by corals, etc. 



E. Land, formed by elevation or a piling up of sand and rubble on the 

 reef. 



F. Lagoon, formed partially by the more rapid growth of the organisms 

 on. the edge of the original bank, building up an encircling reef, and 

 partially by the solution and erosion of the central parts. 



In conclusion, it may be observed that the above remarks 

 apply mainly to the Maldive Group, but it is not unlikely that 

 many of the dominant conditions there will be found to be 

 dominant all over the coral reef area of the Indo-Facific region. 

 I have done no more above than touch on a few of the newest, 

 most important and general points relating to the subject. For 

 a full and detailed account of the coral formations and biologi- 

 cal conditions of the Maldives, I must refer to " The Fauna 

 and Geography of the Maldive and Laccadive Groups " already 

 cited. 



Gonville and Caius College, 

 Cambridge, England. 



